Why did hitler decide to attack the soviet union? what agreement did he break by doing this?

Racial policies of Nazi Germany. As early as 1925, Adolf Hitler vaguely declared in his political manifesto and autobiography Mein Kampf that he would invade the Soviet Union, asserting that the German people needed to secure Lebensraum ("living space") to ensure the survival of Germany for generations to come.

Explanation:

Hitler ordered the invasion of the Soviet Union, which was code-named Operation Barbarossa, on June 22, 1941, deliberately breaking the nonaggression pact that the two countries had signed two years before. The invasion was the largest German military operation of World War II. Battle victories came quickly throughout the rest of 1941, as Germany conquered Soviet-controlled Poland, the Baltic states, and Ukraine. A month after the invasion began, Hitler described his vision for the lands Germany would conquer from the Soviet Union:

The German colonist ought to live on handsome, spacious farms. The German services will be lodged in marvelous buildings, the governors in palaces. . . . What India was for England, the territories of Russia will be for us. If only I could make the German people understand what this space means for our future! Colonies are a precarious possession, but this ground is safely ours. Europe is not a geographic entity, it's a racial entity.

Old Kingdom (about 2,700-2,200 B.C.E.), the Middle Kingdom (2,050-1,800 B.C.E.), and the New Kingdom (about 1,550-1,100 B.C.E.).

Explanation: