When an OSS officer, the late Frank G. Wisner Jr., took over as outpost chief in Bucharest in September, 1944, he realized that the political enemy of the United States would soon be the Soviet Union, not Nazi Germany.

One of the first things Wisner did before the occupying Red Army ordered him to leave Romania in 1945 was to identify Romanians whose political beliefs put them in opposition to the Soviet Union.

Among those on Wisner's list were Romanians who had collaborated with the Nazis. Some were members of the Iron Guard, right-wing zealots who wore dark green breeches and tunics patterned after Gestapo uniforms, who were partly financed by Nazi leader Heinrich Himmler and who rallied round their common hatred of Jews and communists.

From the Office of Strategic Services, Wisner advanced to become chief of the State Department's Office of Policy Coordination in 1947, just after Winston Churchill said that an Iron Curtain had fallen "from Stettin in the Baltic to Trieste in the Adriatic." By that time, Wisner's list of East Europeans whose politics were antithetical to Soviet communism extended from the Baltic to the Black Sea.

It included people from 20 Eastern European jurisdictions, from Estonia, Latvia and Lithuania, from Circassia, Byelorussia and the Ukraine in the Soviet Union. It included Yugoslavians, Albanians, Romanians, Hungarians, Bulgarians and Poles.

It included some accused war criminals who had served in the Latvian Thunder Cross and the Hungarian Arrow Cross as well as the Romanian Iron Guard. It included men who fled the approaching Red Army in 1944 and served the last year of the war in Berlin where they formed their countries' governments-in-exile under Adolf Hitler.

Many of these anti-Soviets were smuggled into the United States in the late '40s and early '50s by Wisner, according to sources involved in a reopened congressional investigation. Just how many came here may never be known, but as many as 5,000 might have been brought in illegally to serve in the mounting propaganda war against Soviet communism, according to the sources.

These illegal emigres were put to work in Radio Free Europe and Radio Liberty, both then financed by the CIA. They also went to work in the Voice of America, the CIA's language school in Williamsburg and the Defense Language Institute in Monterey, Calif., where intelligence officers of the Army, Navy, Marines and Air Force learn the languages of Eastern Europe.

"I like to think of this operation in the image of an hourglass, where at the top of the hourglass are members of Nazi organizations, Nazi collaborators and even accused war criminals," says John Loftus, the former war-criminals investigator at the Justice Department's Office of Special Investigations who exposed the smuggling operation on the CBS-TV program, "60 Minutes," recently.

"In the middle is Wisner's operation at the State Department and then the CIA and at the bottom are the same people who were at the top, except that now they work for the United States in the defense of liberty."

How the Nazi collaborators and war criminals were smuggled to the United States is still a mystery, but it is beginning to unravel. It is partly because Loftus blew the whistle on the smuggling operation and partly because Congress has reopened an investigation--begun in 1977 and closed in 1978--to see if there was a conspiracy in government to obstruct the probes of Nazi war criminals living in the United States.

Congressional sources now believe that Wisner, who committed suicide in 1965, hatched the smuggling scheme while he was OSS outpost chief in Bucharest in 1944 and 1945.

The sources say the General Accounting Office has identified more than 100 men it believes were smuggled into the United States. Only six were German; the rest were Latvian, Ukrainian, Lithuanian, Romanian, Hungarian and Bulgarian. Sources said one was a former senior official of the German Foreign Ministry brought here on orders of CIA director Allen Dulles. The German, an expert on the Soviet Union, was accused of war crimes after leaving the United States in 1953.

A Nazi weapons expert was smuggled here by the Air Force under the guise of Operation Paperclip, which brought Wernher von Braun and his team of V2 rocket experts to the United States. U.S. Army intelligence helped bring in an expert on the Soviet Union who was an officer of the Hungarian Gendarmerie, which persecuted Hungarian Jews with almost the ferocity of the SS and the Gestapo during the war.

Declassified documents of the OSS and State Department now on file in the National Archives show numerous cases of Romanian collaboration with the Nazis. Romania was so loyal to the Third Reich that it was never occupied by the Nazis in the formal sense, and it was an ardent foe of the Soviet Union with anti-Semitism as fervent as any country in Eastern Europe.

Romania passed a law in 1940 declaring Jews "pariahs of the state," by which they lost their property, their homes and even the right to work. Jews were forbidden to attend synagogue services, were denied passports, and were not allowed to own businesses. They were forced to wear the yellow Star of David on their outermost garments, just as in Nazi Germany. More than 300,000 of Romania's 800,000 Jews were deported to the outlying regions of Bucovina and Transnistria, the Siberias of Romania.

By the time the war ended in Romania, more than half of Romania's Jews had been murdered. The entire Jewish population of the city of Dorohoi was taken to the Jewish cemetery and shot. More than 4,000 Jews were massacred in one day in the city of Jassy. Survivors were put into freight cars and transported to the town of Roman without air or water. Most arrived at Roman dead of asphyxiation.

Documents on file at the Archives show that many massacres were carried out by Romanians, not Germans. More than 6,000 Jews were massacred on three days in January, 1941, by members of the Romanian Iron Guard in retaliation for the murder of a German officer by persons suspected of being Romanian Jews. Photographs of the massacre show dead Jews hanging from meat hooks like slaughtered animals.

One Iron Guardist who made an impassioned speech fomenting the massacre was Viorel Trifa, now a bishop of the Romanian Orthodox Church in Detroit who faces deportation after the Justice Department proved that he lied about his membership in the Iron Guard to get here. Trifa's name is on the list of more than 100 suspected Nazi war criminals living in this country that Congress is reinvestigating.

Another name on the congressional list is Nicolae Malaxa, a onetime Romanian industrialist who came to the United States in 1949 on a trade mission for the communist government and stayed until his death 10 years ago. Documents at the Archives show that Malaxa helped to finance the Iron Guard, entered into an agreement with Hermann Goering and his brother Albert to make locomotives and tanks for the Nazis in World War II, and forced his principal Romanian competitor out of the country at the start of the war by a relentless campaign to prove he was a Jew.

Malaxa was defended by Richard Nixon's law firm against deportation proceedings in the 1950s. A private bill to grant Malaxa permanent U.S. citizenship was introduced in Congress by Sen. Pat McCarran of Nevada and Rep. Pat Hillings of California, who had taken Nixon's seat in the House when Nixon moved to the Senate in 1950.

How all this was allowed to take place is the subject of the reopened congressional investigation. In a letter to House Judiciary Committee Chairman Peter Rodino (D-N.J.), the GAO said it plans to submit detailed questions to the State, Defense and Justice departments, the CIA, the FBI and the Immigration and Naturalization Service to find out how many Nazis were smuggled in.

"We have asked these agencies to allow us to have access to all records in their files," the letter to Rodino said. "This would include those documents in their files originated by third parties, including other agencies." It is the opening salvo in an investigation the GAO believes could take as long as five years and may never be complete.