WWII in Colour: Victory in the Pacific Why did Stalin (leader of the Soviet Union) continue to attack after the Japanese surrendered?

Stalin kept attacking because The Soviet invasion came as a fulfilment of Stalin's promise – made to British and American leaders at the Tehran and Yalta conferences – to join the war against Japan following the defeat of Nazi Germany. But it also came in violation of the Soviet-Japanese neutrality pact signed in 1941.

in other words they attacked because Japan technically broke the pact that they had formed between the Soviet union

the tallest building in the western hemisphere and the sixth tallest building in the world