What steps did the major powers take to protect the peace? why did these moves have limited effects?

I believe you are asking about the ww2

The major powers were French and the British, led by Prime Minister Neville chamberlain. They used appeasement policies to prevent war and also to give themselves time to mobilize after a devastating ww1. The policies did not stop Hitler's Germany from militarizing and declaring war on Poland, which sparked the war.