Depends how you look at it. His intel unit found out Soviet Union is amassing a huge invading force at their borders closest to Germany. If I remember correctly, the attack was only weeks away, so he had a choice to either do preliminary attack and take the fight to them, therefore preventing them from gaining any territory in Europe and postponing them getting close to Germany as long as possible, or let them launch a full red tide invasion on Europe. The point is that he was defending his home and his people from direct threat, so it's not really the same as getting your nation involved in a war to protect demon worshippers who never even signed an alliance treaty with US.