Going to War Due to Time Constraints

World Wars 1 and 2 had many causes, some more salient than others.

One kind of cause had to do with a country opting for war because to delay would make fighting enemies in the future more risky.  This was a factor for Germany in 1914 and for Japan in 1941.

In Germany's case, a major potential enemy was the Russian Empire.  Russia was beaten by Japan in their 1904-05 war, but its military was recovering by 1914 and the country was rapidly industrializing.  German army staff planners feared that the Russians, who outnumbered Germans, would probably be considerably more formidable in just a few years.  This consideration helped push an already aggressive German Empire into war.

Japan's case is more complicated to explain.  In brief, the Japanese Empire had been at war with China for a few years.  The year before that conflict began, Japan renounced warship limitation treaties and began increasing the size of its navy.  America began building battleships again around that time, and orders for ships increased as the war in Europe wore on.

Senior Imperial Japanese Navy officers were well aware that the USA could massively out-build Japan in all weapons categories, so renouncing limitation treaties was probably unwise while emotionally satisfying.  As 1941 wore on, the US imposed resource restrictions on Japan, oil and steel in particular, in an effort to persuade Japan to end its war with China.  Expansion-minded Japanese officers who dominated government policy at that time then had the choices of (1) acceding to American wishes, (2) waiting matters out while their petroleum reserves gradually depleted and America launched far more warships than Japan could, or (3) starting war soon while resources were at hand and America's ships were yet to be commissioned.  The third option was selected in the hope that Japan could quickly attain its conquest aims and that then America and Britain would agree to a peace treaty at that point rather than fight a bloody war to the finish.  But the war proved to be long and Japan was crushed by mid-1945.