Did Winston Churchill start the war against the Nazi's?

No. Churchill wasn't even in the British Government at the outset of WW2. (Yes, he was an MP of the governing party) He was a staunch opponent of Naziism & objected to the dealings of the Government by Chamberlain & Lord Halifax among others. The time before Churchill comes to power on the 10th may 1940, coincidentally the German invasion of the low countries & France, was known as his wilderness years.