Relations were also strained with the United States. In November 1964, Kambona publicly announced the discovery of evidence of a U.S.-Portuguese plot to invade Tanzania. The evidence—which consisted of three photostat documents—was labelled a forgery by the U.S. Embassy and after Nyerere returned from a week at Lake Manyara he acknowledged that this was a possibility. After the U.S. launched Operation Dragon Rouge to retrieve white hostages held by rebels in Stanleyville, Congo, Nyerere condemned them, expressing anger that they would go to such efforts to save 1000 white lives while doing nothing to prevent the subjugation of millions of black people in southern Africa. He believed that the operation was designed to bolster the Congolese government of Moise Tshombe, which Nyerere—like many African nationalists—despised. Explaining this antipathy to Tshombe, he said: "try to imagine a Jew who recruits ex-Nazis to go to Israel and assist him in his power struggle. How would the Jews take it?" Relations with the U.S. reached their worst point in January 1965, when Nyerere expelled two members of the U.S. embassy for subversive activities; evidence was not publicly produced to demonstrate their guilt. The U.S. responded by expelling a councillor from the Tanzanian embassy in Washington D.C.; in turn, Tanzania recalled its ambassador, Othman Shariff. After 1965, Tanzanian-U.S. relations gradually improved.