It was definitely the primary attack. That's where First Air Fleet was going and they only had so many carriers. Spread them around and they might have all failed. Midway and Wake were much smaller attacks, but I'm not sure they were quite incidental, weren't they both significant oiling bases? They were certainly both part of Yamamoto's first phase strategy. So were the Philippines, Malaya, and Borneo. Malaya and Philippines were attacked and invaded the same day. Phase 2 would have turned south across territories toward Australia.
His strategy was not too dissimilar to China's today. Loosely to create a huge space of Japanese air space by taking those far flung outposts to ensure any enemy was stretched across thousands of miles of hostile Pacific.
The Battle of Midway, six months later, was one of the most famous and strategically important naval battles of the entire war. As they lost that naval battle it is never really called an attack on the islands, least not in what I've read. They didn't make it that far.
"Midway and Wake were much smaller attacks, but I'm not sure they were quite incidental, weren't they both significant oiling bases?"
They were more significant as refueling stops for transpacific flights, and as projection points for America's air and naval power. Japan wanted to use them for the same purpose, but was unable to; even with the "successful" invasion of Wake Island, the American submarine blockade kept it from being strategically useful to Japan.
Ultimately, the US was able to build up its carrier force enough to offset the need for these force projection points (or at least the need for Wake, given that they didn't retake it until after Japan had already surrendered).
His strategy was not too dissimilar to China's today. Loosely to create a huge space of Japanese air space by taking those far flung outposts to ensure any enemy was stretched across thousands of miles of hostile Pacific.
The Battle of Midway, six months later, was one of the most famous and strategically important naval battles of the entire war. As they lost that naval battle it is never really called an attack on the islands, least not in what I've read. They didn't make it that far.