OPINION OF THE COURT
ROSENN, Circuit Judge.
The Government instituted proceedings in the United States District Court to revoke and set aside an order admitting the defendant, Serge Kowalchuk, to citizenship because his naturalization had been illegally procured by concealment of a material fact or by willful misrepresentation.1 In essence, the complaint alleged that the defendant failed to disclose in response to questions during the admissions procedure certain material facts: his membership in and employment by the Ukrainian militia and his residence in Lubomyl, Poland, during the war years 1941 and 1942. The [490] complaint thus alleged that he entered this country unlawfully, procured his permanent residence by fraud, and obtained his naturalization illegally.
The district court, 571 F.Supp. 72, concluded that the defendant illegally procured his citizenship by entering this country with an invalid visa. It had two separate grounds for this conclusion. First, the defendant was not a genuine refugee of concern to the International Refugee Organization (IRO) and therefore was ineligible for admission under the Displaced Persons Act of 1948 (DPA), Pub.L. No. 80-774, 62 Stat. 1009 (1948) (codified at 50 App.U.S.C. §§ 1951-1965 (1982)). Second, the defendant was ineligible under section 10 of the DPA because he had made material misrepresentations to obtain the visa. The court accordingly revoked the defendant’s citizenship and canceled his certificate of naturalization. We affirm.
I.
These revocation proceedings have their genesis in Serge Kowalchuk’s activities shortly after the German military forces occupied Lubomyl in June 1941. Within two or three weeks after occupation, the Germans organized the Ukrainian schutz-mannschaft.2 Shortly thereafter, the defendant, then an able-bodied twenty-one year old man, suitable for military service, successfully sought out the collaborating mayor of the city for employment.
His first assignment was to the food distribution center serving government employees and the militia. He apparently was in charge, for the only other employee there was his assistant. In about one and one-half months, he was assigned to the schutzmannschaft headquarters across the street. He worked at the food distribution center in the mornings and at militia headquarters in the afternoons. Apparently impressed by his services, his superiors, in August 1941, sent the defendant, according to his testimony, elsewhere for special training at no expense to him. He was the only selectee from the Lubomyl area in a class of between 45 and 50. Upon the conclusion of his six months “additional training in local administration” and German language study, he received a certificate of completion and returned to his duties with the Lubomyl schutzmanns-chaft. His duties now were full time with the militia3 until he fled Lubomyl with the retreating Germaii army. As was the case with only the commandant and deputy commandant, defendant had his own private office and occupied these quarters for almost three years, the remainder of the Nazi occupation.
A.
To fully appreciate the defendant’s role with the schutzmannschaft, an understanding of its function and its crucial importance to the Germans in carrying out the policies of the German army in the Ukraine may be helpful. The Germans organized indigenous personnel and formed them into auxiliary forces. They organized the Lubomyl schutzmannschaft into precisely such a body. These auxiliary forces enabled the Nazis to carry out their repressive and brutal policies and, at the same time, to wage an aggressive military campaign. As the district court found, “the occupying authorities did rely upon ‘indigenous forces,’ i.e., segments of the local population, to carry on the functions of government and to enforce the observance of restrictive edicts.” United States v. Kowalchuk, 571 F.Supp. 72, 80 (E.D.Pa.1983).
According to Professor Raul Hilberg, a leading authority on the Holocaust produc[491] ed as an expert witness by the Government at trial, “the availability of an auxiliary force made of Ukrainian personnel was of crucial importance to the Germans, particularly because without them nothing at all could have been accomplished” in carrying out the policies of the German army in the occupied territories. Dr. Hilberg further testified that the sheer numbers of those killed in the liquidation of the Jews required the use of indigenous personnel. As the district court found, the magnitude of the brutal plan to liquidate in one day the 5,000 to 6,000 Jews living in Lubomyl required not only the German soldiers available, but also “significant numbers of Ukrainian militiamen to assist them in escorting the Jews from the ghetto to the execution site, and to prevent escapes.” United States v. Kowalchuk, 571 F.Supp. at 81. The district court found
What the evidence does establish with the requisite clarity and conviction is that the Lubomyl schutzmannschaft regularly and routinely enforced the martial law restrictions imposed by the Germans, including beating Jews found outside the ghetto after curfew, beating or severely reprimanding Jews who failed to wear the required insignia, assisting the Germans in confiscating valuables from the Jewish inhabitants, arresting and participating in the harsh punishment of persons involved in black-market activities or subversive activities hostile to the German occupation forces; and that the defendant was aware of the responsibilities assigned to the schutzmannschaft, and occupied a responsible position, albeit largely clerical, within that organization.
... It is apparent ... that members of the schutzmannschaft accompanied the German gendarmes on the many occasions disclosed by the testimony when persons were rounded up for forced labor, or arrested for various supposed infractions; that many of the persons thus apprehended were killed soon afterward; and that members of the schutz-mannschaft were present during such executions.
571 F.Supp. at 81.
The district court concluded that although the evidence did not disclose, with the requisite clarity, that the defendant personally participated in any individual atrocities,4 the court nonetheless found:
[T]he evidence as a whole leaves little doubt that everyone associated with the schutzmannschaft, including the defendant, must have known of the harsh repressive measures which the schutz-mannschaft were carrying out pursuant to German direction.
571 F.Supp. at 81.
B.
When the Germans retreated from the Ukraine, the defendant elected to flee with them to Czechoslovakia.5 The defendant [492] and his younger brother, Mykola, ultimately arrived at a displaced persons camp near Salzburg, Austria. After spending four years there, the defendant applied in November 1947 for the necessary clearance certifying that he was a refugee “of concern” to the IRO. To obtain this certification, the defendant executed a required detailed personal history form (the CM/1 form). The defendant stated on this form that during the German occupation of the Ukraine, he lived in Kremianec, not Lubo-myl, and that he worked there as a tailor. He concealed his service with the Lubomyl militia during the war. The district court found: “In his CM/1 personal-history form, the defendant intentionally misrepresented and/or concealed his residence in Lubomyl and his employment with the town government there during the German occupation.” 571 F.Supp. at 81.
The defendant then took the next step to gain admission to the United States as a permanent resident. For this purpose, he submitted an additional personal history questionnaire, the “fragebogen,” together with his IRO documentation, to representatives of the United States Displaced Persons Commission (DPC). After the required investigation, he was duly certified in 1949 as meeting the eligibility requirements of the DPA. He then applied to the vice consul of the United States at Salzburg, Austria, and on December 29, 1949, he obtained a visa for admission to the United States for permanent residence. His petition for naturalization was granted on November 30, 1960, and he was admitted to citizenship.
The fragebogen opened with the admonition that “all questions must be answered and all information must be complete” and concluded with Kowalchuk’s signature and his attestation that “if it is found to be untrue, incomplete, or misleading in any point, I may be denied entry into the United States.”
Kowalchuk’s responses to the fragebo-gen were false and misleading in the following respects: (1) Kowalchuk concealed his membership in the Ukrainian schutz-mannschaft by falsely stating that .he was a tailor’s assistant in Kremianec from 1939 to 1944. (2) He concealed his residence in Lubomyl by falsely stating that he had lived in Kremianec from 1939 to 1944. (3) He only listed attendance at a trade school in Chelm, Poland, between 1936 and 1939 and concealed the fact that he was sent, as he now claims, for special schooling in 1942 and 1943 by the Nazi-controlled government of Lubomyl. (4) He concealed his voluntary departure with the retreating German military forces from Lubomyl to Czechoslovakia, by falsely stating that he left his homeland because he was forcibly transported by the Germans. (5) In response to a question concerning membership in any political, non-political, or paramilitary organization, he falsely replied “none,” thereby concealing his membership in the schutzmannschaft.6
II.
On appeal, Kowalchuk argues that the district court committed reversible error in two respects: (1) its legal conclusions are not supported either by its own factual findings or by the evidence of record; and (2) his due process rights were violated because he was unable to investigate and interview “potentially favorable witnesses to him” residing in Soviet-controlled territory.
The Government sued under section 340(a) of the Immigration and Nationality Act of 1952, as amended, 8 U.S.C. § 1451(a) (1982) to have Kowalchuk denaturalized. This statute provides for the revocation of an order admitting a person to citizenship if such order and naturalization certificate “were illegally procured or were procured by concealment of a material fact or by willful misrepresentation.” To obtain a [493] grant of citizenship legally, an applicant must have resided in the country for at least five years after having been lawfully admitted for permanent residence pursuant to a valid visa. 8 U.S.C. §§ 1181(a) and 1427(a)(1) (1982).
Kowalchuk entered the United States under a visa issued pursuant to the DPA quota structure at that time. The DPA permitted increased immigration into the United States of eligible persons displaced by World War II. To gain lawful admission to the United States for permanent residence under the DPA, the applicant first had to establish that he was a displaced person or a refugee of concern to the International Refugee Organization (IRO). See DPA, § 2(b). The IRO guidelines excluded from their concern any person who either “assisted the enemy in persecuting civil populations ...” or “voluntarily assisted the enemy forces ... in their operations against the United Nations.” Finally, the DPA provided that anyone who made a willful misrepresentation for the purpose of obtaining a visa would be inadmissible. Thus, a person not eligible for refugee or displaced person status under the IRO Constitution or guidelines or who had made a material misrepresentation on his visa application could be denaturalized under section 1451(a). See Fedorenko v. United States, 449 U.S. 490, 101 S.Ct. 737, 66 L.Ed.2d 686 (1981).
III.
Because citizenship in this nation is a precious right, once conferred, the Government bears “a heavy burden of proof” in a denaturalization proceeding. Costello v. United States, 365 U.S. 265, 269, 81 S.Ct. 534, 536, 5 L.Ed.2d 551 (1961), quoted in Fedorenko v. United States, 449 U.S. at 505, 101 S.Ct. at 746. To revoke a grant of citizenship, the evidence must be clear, unequivocal, and convincing. Schneiderman v. United States, 320 U.S. 118, 125, 63 S.Ct. 1333, 1336, 87 L.Ed. 1796 (1943); see also United States v. Riela, 337 F.2d 986, 988 (3d Cir.1964). “Any less exacting standard would be inconsistent with the importance of the right that is at stake____” Fedorenko v. United States, 449 U.S. at 505-06, 101 S.Ct. at 747.
Although the burden of proof upon the Government in a denaturalization proceeding is heavy, a certificate of citizenship is not immune from challenge. It is “an instrument granting political privileges, and open like other public grants to be revoked if and when it shall be found to have been unlawfully or fraudulently procured.” Johannessen v. United States, 225 U.S. 227, 238, 32 S.Ct. 613, 615, 56 L.Ed. 1066 (1912). As the Court in Fedorenko aptly observed, the cases have also recognized that an applicant for citizenship must strictly comply with all the congressionally imposed prerequisites to the acquisition of citizenship.
Failure to comply with any of these conditions renders the certificate of citizenship “illegally procured,” and naturalization that is unlawfully procured can be set aside. As we explained in one of these prior decisions:
An alien who seeks political rights as a member of this Nation can rightfully obtain them only upon terms and conditions specified by Congress ...
“No alien has the slightest right to naturalization unless all statutory requirements are complied with; and every certificate of citizenship must be treated as granted upon condition that the government may challenge it ... and demand its cancellation unless issued in accordance with such requirements.”
Fedorenko, 449 U.S. at 506, 101 S.Ct. at 747 (quoting United States v. Ginsberg, 243 U.S. 472, 475, 37 S.Ct. 422, 425, 61 L.Ed. 853 (1917)) (additional citations omitted).
IV.
Kowalchuk’s first step to lawful entrance into the United States as a permanent resident under the DPA required that he establish himself as a displaced person [494] or refugee of concern to the IRO. The district court found that the defendant was not “of concern to the IRO” because he “voluntarily assisted the enemy forces,” a determination that, under the Constitution of the IRO, would have excluded the defendant from eligibility as a bona fide refugee or displaced person. Section 2(b) of the DPA incorporated the definition of a displaced person set forth in the IRO Constitution. Michael R. Thomas, chief eligibility officer for the IRO in 1948, and co-author of the IRO Manual for Eligibility Officers, testified that membership in a police force or militia raised a presumption of voluntary assistance to the enemy. These forces “freed the enemy from using its own people.” A.P. Conan, employed by the DPC between 1948 and 1952, served a stint as a senior officer in charge of the commissioner’s activities for the British Zone. He essentially reviewed the eligibility of those whose applications the Commission proposed to reject. He testified that an applicant who had served in the Ukrainian schutzmannschaft would have been rejected unless he overcame the presumption against his eligibility by showing that his service was involuntary, and that he had not committed atrocities or persecuted any person on the ground of religion, race, or national origin.
Professor Raul Hilberg testified that the “German forces were totally insufficient to undertake the policies of Nazi Germany in the occupied territories,” and that the assistance of an auxiliary force of Ukranian personnel was “of crucial importance.” The importance of those forces was acknowledged by the IRO, which in Part II Appendix IV of Provisional Order 42 defined “enemy forces” to include “police, paramilitary and auxiliary organizations.” The district court also observed:
It is impossible to avoid the inference that the defendant had found favor with the Nazi occupiers of Lubomyl, and was being trained for even greater service in the future.
If the defendant’s activities had been innocuous as he claims, there would have been little reason for him to leave Lubo-myl with the retreating Germans.
571 F.Supp. at 76.
The provisions of the IRO constitution,7 and the testimony of Thomas, Conan, and Hilberg support the district court’s findings and convincingly demonstrate that the defendant’s voluntary membership in the Ukrainian schutzmannschaft constituted voluntary assistance to the enemy.
The district court also found that Serge Kowalchuk “assisted the enemy in persecuting civilian populations,” an alternative basis for its conclusion that the defendant was not a bona fide refugee of concern to the IRO. We do not need to reach this issue. Thus, the defendant’s citation to U.S. v. Sprogis, 763 F.2d 115 (2d Cir.1985) is irrelevant.
V.
A grant of citizenship may also be revoked if it was “illegally procured or ... procured by concealment of a material fact....” 8 U.S.C. § 1451(a) (1982). Unless the preconditions to naturalization are met, citizenship is “illegally procured” and may be revoked. Fedorenko v. United States, 449 U.S. 490, 506, 101 S.Ct. 737, 747, 66 L.Ed.2d 686 (1981). To obtain a grant of citizenship, an applicant must have entered the United States pursuant to a valid visa. An applicant ineligible under the law may not obtain a valid visa.
Kowalchuk obtained his visa and entered this country under the provisions of the DPA. The Act enumerated certain auto[495] matic exclusions from eligibility. 10 stated: Section
No eligible displaced person shall be admitted into the United States unless there shall have first been a thorough investigation and written report ... regarding such person’s character, history, and eligibility under this Act. The burden of proof shall be upon the person who seeks to establish his eligibility under this Act. Any person who shall willfully make a misrepresentation for the purpose of gaining admission into the United States as an eligible displaced person shall thereafter not be admissible into the United States. (Emphasis added.)
In this case, it is undisputed that Kowalchuk “wilfully ma[d]e a misrepresentation for the purpose of gaining admission into the United States as an eligible displaced person.” Kowalchuk argues, however, that the misrepresentations about his wartime activities were not “material.”8 We disagree.
A.
In Chaunt v. United States, 364 U.S. 350, 81 S.Ct. 147, 5 L.Ed.2d 120 (1960), the Government attempted to revoke the petitioner’s citizenship on the ground that he had made several misrepresentations in his application for citizenship. The district court cancelled the petitioner’s naturalization, and the court of appeals affirmed. The Supreme Court reversed, finding that Chaunt’s misrepresentations were not ma-ferial. At issue was Chaunt’s failure to reveal arrests that were made more than five years prior to the time of naturalization. The Court stated that “[t]he totality of the circumstances surrounding the offenses charged makes them of extremely slight consequence,” id. at 354, 81 S.Ct. at 150 and therefore would not of themselves have provided a ground to deny citizenship. The Court also rejected the Government’s argument that had it known of the arrests it might have investigated Chaunt further and might well have discovered a link between him and the Communist Party, explaining that the information that Chaunt had disclosed revealed a more substantial nexus with the Communist Party than the undisclosed arrests did. Id. at 355, 81 S.Ct. at 150.9 The Court then concluded that the decision to denaturalize Chaunt should be reversed because
the Government ... failed to show by “clear, unequivocal, and convincing” evidence either (1) that facts were suppressed which, if known, would have warranted denial of citizenship or (2) that their disclosure might have been useful in an investigation possibly leading to the discovery of other facts warranting denial of citizenship.
Id. at 355, 81 S.Ct. at 150-51.
The Court in Chaunt thereby devised a two-pronged test for materiality in denatu-ralization eases. Under the first prong, the Government must prove that a truthful answer to a question “would have warranted denial” of the application. In the alter[496] native, the Government may prevail under the second prong. The second prong deals with a situation in which the truthful answer to a question would not by itself warrant the disqualification of the applicant. The Government may still demonstrate that the misrepresentation is material if it shows that the truthful answer “might have been useful” in an investigation of the applicant “possibly leading to the discovery of other facts warranting denial of citizenship.” Chaunt, 364 U.S. at 355, 81 S.Ct. at 151.
In United States v. Fedorenko, 449 U.S. 490, 101 S.Ct. 737, 66 L.Ed.2d 686 (1981), the Supreme Court affirmed the court of appeals’ decision ordering Fedorenko’s denaturalization. Without deciding the question of whether the Chaunt materiality test also governed false statements in visa applications, the Court reasoned: “At the very least, a misrepresentation must be considered material if disclosure of the true facts would have made the applicant ineligible for a visa.” Id. at 509, 101 S.Ct. at 749.
In United States v. Koziy, 728 F.2d 1314 (11th Cir.), cert. denied,-U.S.-, 105 S.Ct. 130, 83 L.Ed.2d 70 (1984), the district court found that Koziy had failed to reveal in his visa application that he had been a member of the Ukrainian police. In affirming the revocation of Koziy’s citizenship, the court of appeals stated:
The district court found that Koziy never disclosed his membership in the Ukrainian Police Force. It ruled that if he had disclosed his connection with the police force in his visa application, his application would have been rejected out-right____ These findings are not clearly erroneous.
Id., 105 S.Ct. at 1320.
B.
Had Kowalchuk revealed the facts which he suppressed on December 29, 1949, the day he obtained his visa, those facts would have warranted the denial of his visa and thereby precluded him from obtaining citizenship. As previously noted, the defendant willfully concealed his voluntary membership and employment in the Ukrainian militia/police force, his residence at Lubo-myl, his attendance at the special training school during the German occupation, and his voluntary flight to Czechoslovakia with the retreating German military forces. See footnote 6 supra. As Michael R. Thomas, chief eligibility officer for the IRO, testified, supra, at 494, the DPC would accept only those refugees who were eligible for IRO assistance, and that an applicant who had voluntarily assisted the enemy force would be ineligible.10 An applicant who reported that he belonged to a police force or militia (regardless of his function in the organization) would have been presumed to have voluntarily assisted the enemy. The applicant had the burden of proving eligibility for IRO assistance and his CM/1 form became the basic document upon which the field officer depended.
Conan, the DPC’s senior reviewing officer of proposed reject applications for entry into the United States, also testified, supra, at 494. He stated that an applicant who reported that he had served in the Ukrainian schutzmannschaft would have been rejected unless he were able to prove that he served involuntarily and that he was not involved in persecution of civilians. This testimony is fully consistent with the IRO Manual for Eligibility Officers. A schutzmannschaft member who was unable to overcome the presumption would have been rejected even though the Ukrainian schutzmannschaft was not on a list of inimical organizations. (A 1512-13) Government exhibits demonstrate that applications in fact had been rejected in 1952 by [497] the DPC under section 1311 of the Act on the ground of such membership. Moreover, Conan testified that applications of members of the Ukrainian schutzmanns-chaft would have been rejected prior to the 1950 amendment of the DPA.
John Chapin, American vice-consul in 1948 in Salzburg, Austria, testified that the IRO documents, the attested fragebogen, and the DPC’s investigation and report accompanied the application for a visa. The standard procedure in every case was for the American vice-consul to read the frage-bogen, personally interview the applicant concerning wartime residence and occupation, and to have the applicant swear to the truth of all the statements in the application, including the fragebogen. (A 1032-33) Close attention was paid to the applicant’s occupation and residence during the war years and the applicant had the burden under the law of proving eligibility for a visa. Persons who had served in the Ukrainian police or militia would have been ineligible.
Whatever the defendant’s motivation,12 the misrepresentations and concealment were material to the IRO’s determination in 1947 of whether Kowalchuk was a bona fide refugee and “of concern” to the IRO. They were plainly material to the vice consul’s determination in 1948 that Kowalchuk was eligible for admission to the United States as a permanent resident. The evidence of willful misrepresentation, concealment, and materiality is clear, convincing, and unequivocal. Regardless of whether the defendant personally participated in the atrocities and brutalities committed by the Lubomyl schutzmannschaft, the district court found that the “defendant was aware of the responsibilities assigned to the schutzmannschaft, and occupied a responsible position, albeit largely clerical, within that organization.” 571 F.Supp. at 81. Truthful answers on the CM/1 and the fragebogen would have prevented the defendant from obtaining a visa under the DPA.
Because we conclude that disclosure of the true facts concerning defendant’s wartime activities would have made him ineligible for a visa, we find it unnecessary to resolve the question of whether defendant’s misrepresentations were material under the second prong of the Chaunt test. See Fedorenko v. United States, 449 U.S. at 509, 101 S.Ct. at 748.
VI.
The defendant also contends that he was denied due process. He asserts that when his counsel was in the Soviet Union for the depositions of the government witnesses, the Soviet Union denied him the opportunity to visit Lubomyl to investigate or interview potential witnesses. However, as the district court observed, Soviet Russia also imposed the same limitations upon Government counsel. The defendant does not make any claim that he was deprived of any specific evidence or testimony. He makes no showing that any testimony has been excluded that “would have been material and favorable to his defense.” United States v. Valenzuela-Bernal, 458 U.S. 858, 867, 102 S.Ct. 3440, 3446, 73 L.Ed.2d 1193 (1982).
At one point, defense counsel informed the Government that he knew of eighteen witnesses in the Soviet Union whom he would like to call. Yet, he made no request to interview any of them or to depose them. On the other hand, the Government by letter dated March 12, 1980 informed defense counsel that it was requesting permission from the Soviet Union to bring the deposed witnesses to the United States to testify and offered “to make a similar re[498] quest on behalf of the Kowalchuks that specific witnesses be produced to testify on their behalf.” The defense failed to follow through on the Government’s offer. Their request to interview witnesses was made only after defense counsel was in the Soviet Union and even then it was made informally. Moreover, the trial court’s factual conclusions are based upon the testimony of the defendant and his witnesses or other evidence not inconsistent with that testimony. 571 F.Supp. at 80.
We see no merit to the defendant’s due process contention.
VII.
In sum, the district court revoked the defendant’s citizenship on the following independent grounds: (1) the defendant was not a genuine refugee “of concern” to the IRO and therefore was not entitled to the benefits of the Displaced Persons Act because (a) as a member of the schutzmann-schaft he voluntarily assisted the enemy forces in their operations against the United Nations, and (b) in such capacity he assisted the Nazis in persecuting civilians, and (2) the defendant illegally obtained his visa because he made willful material misrepresentations to gain admission to the United States as a permanent resident.
Although we do not decide whether the record supports the district court’s conclusion that the defendant assisted the enemy in persecuting civilians, we hold that the record fully supports the trial judge’s findings and his conclusions concerning the defendant’s voluntary assistance to enemy forces and his willful material misrepresentations.
Accordingly the judgment of the district court will be affirmed.