Shinto revolves around veneration of spirits (both of ancestors and 
things around them) I don't think that it has ever been a rallying 
point for a religious war or anything. Unlike western religions as 
far as I can tell it was never really a centrally organised religion.

Unless you count State Shinto of recent history.

"Because of its close ties to the militarism that led to World War II, 
State Shinto as a national organization was disestablished in 1945 by the 
Allied Occupation." 
--Gateway to Japan, revised ed., pub. Kodansha

Japan was under 'Militarism' for the Meiji Period (1868-), which used 
Shinto, changed into State Shinto (during the previous Edo period, by 
nationalists), as a state religion. So Shinto, altered, was involved in 
Japan's imperialist invasions of Taiwan, Korea, Manchuria, and later, 
most of SE Asia and more of China. Personally, I think the worst 'bad 
stuff' of the time was the extreme racism of the Japanese Army - 
generally acknowledged today in Japan, (at least by the public, if not 
the government or, *especially*, the Education Ministry) although very 
quietly, in comparison with Germany - but how much State Shinto had to do 
with this I have no idea. 

State Shinto far right wing nationalists (militarists? - all these terms 
always go together in Japan, it seems) - still demonstrate in Tokyo 
today, but they seem like a tiny fringe group to me, although I don't 
know that much about current Japanese politics.