This is something that always baffled me about WW2. Nazi Germany and Japan are on opposite sides of the world, and have no common fronts and few if any common enemies. They don't seem to have had any kind of central organization or coordinated strategy together, and in even in some ways had somewhat contradictory goals. Why did they end up being on the same side of the war, instead of two separate conflicts?

When Japan then attacked Pearl Harbor in 1941, the United States then followed by declaring war on Germany, as if they had anything to do with it. Surely Hitler could have simply denounced Pearl Harbor, severed all relations with Japan, tear up the tripartite pact, and lose absolutely nothing.

Part of what always makes World War Two so impressive is the scale of fighting, having an equal amount of intense conflict on polar opposite ends of the globe. But at that same time, that very premise is rather counter-intuitive to wrap one's mind around. Since it seems that aside from this single, verbal alliance between Japan and Germany, there doesn't appear to be anything to really connect these two hemispheres together.

Edit: Before I go to bed, I want to shout out to the 500 people who pointed out that Germany declared war on America first, the day after Japan did. Although I did not know that, that doesn't really change my question whatsoever. Of course, I could have said this a while ago to clear up the confusion, but I liked the chaos.