On 12 September 1946, Pearson wrote an article based on a classified US military study of British military operations against the Greek Communist insurgency. The article, which alarmed the U.S. State Department, contained highly classified information on the British order of battle in Greece. The document had been in the office of the Director of the Office of Special Political Affairs, one Alger Hiss. An investigation revealed that the original document was missing and that the information reached Pearson through his aide, David Karr. The FBI suspected that Karr was working for the KGB and that his income was derived in part from the Soviet government.