Carl Emil Ludwig Krepper (May 11, 1884 – June 21, 1972) was a German-American Lutheran pastor and Nazi collaborator who assisted the Nazi saboteurs in Operation Pastorius during World War II.

Early life 
Krepper was born in Altona, Hamburg. He attended the Ebenezer Seminary, which trained Lutheran clergy, at Kropp in Schleswig-Holstein. In 1909, Krepper moved to the U.S., where he was naturalized. He served at Lutheran churches in Newark, Rahway, Carteret, and Bridgeton. He later earned a master's degree from Rutgers University. In his master's thesis, Krepper was very critical about the U.S. and of the church for not being outspoken against slavery during the American Civil War.

Nazi collaboration 
At the same time, however, Krepper became a fanatical Nazi. He was a member of the German American Bund and the German American Business League, which supported boycotting Jewish businesses. In 1935, Krepper went to Germany. He returned to the U.S. as a spy in 1941. In 1942, during Operation Pastorius, Krepper helped establish safehouses in New Jersey for the saboteurs of the mission. His name was one of several written on handkerchiefs given to George John Dasch and Edward Kerling.

Due to a lack of evidence, Krepper was not arrested when the plot was exposed by Dasch and Ernest Peter Burger. In December 1944, he was arrested after a sting operation by the Federal Bureau of Investigation. J. Edgar Hoover had wanted to use Krepper as a double agent, but was unsuccessful due to Krepper's commitment to Nazism. In February 1945, Krepper was found guilty on one count of trading with the enemy, for which he faced up to 20 years in prison. The following month, he was also found guilty of conspiracy to commit sabotage and violate wartime censorship laws, for which he faced up to two years in prison.

Krepper was ultimately sentenced to 12 years in prison. He was sent to the United States Penitentiary in Lewisburg, Pennsylvania to serve his sentence. The government also charged Krepper with three additional counts of conspiracy, for which he faced up to 32 more years in prison. However, the charges were dismissed, albeit Krepper's appeals against his initial convictions were unsuccessful.

Krepper was paroled on February 3, 1951. Further attempts by him to secure a pardon or have his conviction overturned failed. He remained on parole until 1957. Krepper moved to the Berkshires, where one of his girlfriends owned property. He managed to secure Social Security benefits and a pension from the German Lutheran Church. Krepper died of bronchopneumonia at a nursing home in Great Barrington, Massachusetts on June 21, 1972.

References 

1884 births
1972 deaths
Antisemitism in the United States
American collaborators with Nazi Germany
American prisoners and detainees
Christian fascists
20th-century American Lutheran clergy
German Lutheran clergy
German emigrants to the United States
Deaths from bronchopneumonia
People from Altona, Hamburg
Protestant religious leaders convicted of crimes
Prisoners and detainees of the United States federal government