the authorities as "workers". An internal attempt was made to discredit Gomułka's leadership, but there were aspects of the ongoing witch hunt which he found to be to his advantage and tolerated. In the meantime, irreversible damage to society had been wrecked by the Moczar movement. Gomułka's regime reasserted itself and was saved by a combination of international and domestic factors, including the Moczar faction's inability to take over the party and state apparatus. The Soviet Union, now led by Leonid Brezhnev, was preoccupied with the crisis in Czechoslovakia and not inclined to support personnel changes in the Polish leadership. In August 1968, the Polish People's Army took part in the Warsaw Pact invasion of Czechoslovakia. Some Polish intellectuals protested, and Ryszard Siwiec burned himself alive during celebrations of an official holiday. The Polish participation in the crushing of the Czech liberalization movement (the crowning achievement of Marxist revisionism, according to David Ost) further alienated Gomułka from his former liberal supporters. But within the party, the opposition to Gomułka faded and the 5th Congress of the PZPR reconfirmed his rule in November. Brezhnev, who attended the gathering, used the occasion to expound his Brezhnev Doctrine, a self-granted Soviet right to forcefully intervene if an allied state strays too far from the "fraternal course". Treaty with West Germany, food riots and the ousting of Gomułka In December 1970, Gomułka's government scored a major political success when Poland obtained recognition by West Germany of post-World War II borders. In the negotiations leading to the Treaty of Warsaw, the German side secured the right to emigrate to West Germany for residents of Poland of German identity and the ability to help financially those who stayed in Poland by granting pensions. Hundreds of thousands eventually became affected. German Chancellor Willy Brandt, who signed the agreement, used the occasion to ask on his knees for forgiveness for the crimes of the Nazis (Kniefall von Warschau). His gesture was understood in Poland as being addressed to all Poles, although it was made at the site of the Warsaw Ghetto and thus directed primarily toward the Jews. The notable reconciliation process between the Polish and German nations was initiated five years earlier, when the Polish Church leaders issued the Letter of Reconciliation of the Polish Bishops to the German Bishops, criticized then by the Polish government. Gomułka felt proud and secure after the treaty with West Germany,