The Annie Larsen affair was a gun-running plot in the United States during World War I.[1] The plot, involving India's Ghadar Party, the Irish Republican Brotherhood and the German Foreign office, was a part of the larger so-called "Hindu–German Conspiracy",[2] and it was the prime offence cited in the 1917 Hindu–German Conspiracy Trial, described at the time as the longest and most expensive trial in American legal history.[3]