That’s right.
After Pearl Harbor, Yamamoto said he could win some battles for 6 months to a year and then it would be difficult. He knew it was hopeless.
I think they were only thinking about a quick, devasting destruction of American Naval capability caught at Pearl Harbor so that the US would relent and ease their embargoes and restrictions against Japan and let them take the South Pacific/Asia for resources as they had been.
Their mistake was twofold. 1) Their spying did not account for the absence of three American Carriers (IIRC) based out of Pearl Harbor, and 2) Yamamoto’s failure to launch additional waves of planes while they had the chance for fear of their A/Cs being discovered.