call me crazy but i feel like if you declare war on a sovereign nation then you are the one who caused a war with a sovereign nation. especially if you follow it up by sending a few hundred thousand troops across their borders to start killing people and capturing cities and such.
"but they wouldn't let us dictate their foreign policy!!!!!!!!" is a justification, i guess, but it's kind of a bad one imo imho.
lol let me guess — you're a huge fan of neville chamberlain