(ANSA-AP) - WARSAW, Poland — Polish officials joined war veterans on Sunday to pay tribute to a World War II-era underground force that collaborated with Nazi German force toward the end of the war in their battle against the Communists, who were imposing control on the nation. A Mass in Warsaw opened ceremonies honoring the Holy Cross Mountains Brigade of the National Armed Forces on the 75th anniversary of its formation. President Andrzej Duda's official patronage and the presence of ruling party officials underlined the right-wing government's rehabilitation of a partisan unit that fought both Germans and Soviets and which is celebrated by the far right. It is seen as a part of a broader attempt by the ruling Law and Justice party to appeal to right-wing voters ahead of the nation's parliamentary vote in October. Poland had a large underground Home Army under the command of a government-in-exile that never collaborated with the Germans and remembrance ceremonies traditionally focus on those soldiers. The official rehabilitation of the Holy Cross Mountains Brigade began when Prime Minister Mateusz Morawiecki honored them at a cemetery in Munich in February 2018. On the same day that he asserted at a news conference that there were some "Jewish perpetrators" of the Holocaust. Sunday's ceremonies were criticized by the children of Polish resistance fighters. Some of them wrote in a letter to Duda saying "our fathers fought against the Nazis because they understood their duty toward their homeland. Any cooperation with the occupiers was unimaginable to them." Poland's chief rabbi also rejected an invitation to Sunday's ceremony, calling it "a personal insult." (ANSA-AP).