“9 May 1945” — Czech postcard celebrating the Red Army's arrival in Prague on 9 May, 1945. In the illustration, a Red Army soldier stands on a torn Nazi flag while offering his hand to a kneeling woman wearing the coat of arms of Bohemia and Moravia.
The Red Army arrived in the wake of the Prague Uprising that had all but wiped out the German presence in the city. The uprising began spontaneously on the 5 May and led to four days of brutal fighting, ending with the Soviets' arrival. The Red Army suffered only 10 casualties.
These postcards appear to be from the same series, possibly published in 1946. In this one, a man tears the Nazi flag while the Allied flags fly overhead and a rainbow arches over Prague in the background. The illustrations were apparently done by Czech artist Otto Ušák.
In this one, men march while Stalin and President Edvard Beneš loom behind. Beneš served as President of Czechoslovakia from 1945 until 48 (as well as through the 30s).
"Victory Day" — 9 May would subsequently be celebrated each year as Victory Day in communist Czechoslovakia.