Was there any big gas warfare in WWII and what about mustard gas?

All Wehrmach soldiers have that iconic cylindrical gas mask container, but unlike WWI I have never heard of any use of poison gas in European theater of war (I mean in battles, not in concentration camps). Were there any major battles that used gas in WWII? And what about mustard gas? Reason I mention this is that in one of episodes from The Great War, Indy mentioned that Hitler didn’t like that in particular so much to ban it later in WWII. Is that true? Because, well, WWII used much deadlier gasses, so why did Hitler just had aversion to mustard gas?