Haven't they all been wartime presidents?
Of course. Every president not only has wars, but starts his own war. It's normal. Even Clinton started the war in Serbia ---- and won it quickly, which is a lot more than I can say about any presidents since then.
It seems obvious that we'll be attacked by North Korea (which does seem to think they can win, never a good sign -- think of when the Japanese thought that) and very likely Iran, perhaps with strong proxy attacks on Israel and Syria, already probably begun.
However, it's never the most obvious countries. Look at all the wild cards -- Reagan with Grenada (the Cubans were putting in a military airfield) and Iran; Bush I with a sudden move on Kuwait by Iraq; Clinton with a war on Serbia???? that was weird, but at least he wasn't fool enough to get us involved in Rwanda; Bush II blindsided by 9/11. Obama didn't start his own war exactly but he did keep ALLLLLLLL the old ones going endlessly and losing.
So we do have to expect a war. Could be the obvious suspects, but it could be Iceland or Venezuela or Russia. I am especially keeping my eye on Pakistan.