Sorry about the misunderstanding about the Seals.
I dwelt on Eisenhower because he was brought up by jc, and the only thing I could find in the book he cited that might have questioned FDR's judgment was about the Phillipines.
In re the rest, a little Constitutional background: the Prez is supposed to be very constrained in his command of the military. It was never envisioned that wars would be fought without a declaration from Congress.
The design of the Federal government was that Congress, the lower house at that, raises the actual money. So, no President could raise money for an army without them. Congress also declares war. If you go back and look, you'll also notice there's a very interesting sunset clause in appropriations for an Army: they had to be renewed every two years, at least, by the Congress. Because, of course, the term of a Congressman is two years. So, if an army was to be supported by tax dollars, a Congressman had to vote that appropriation for that army up or down at least once in his term.
No such clause exists for the Navy, since they were seen as essential to the defense of the country and its international interests. Invasion by land would be taken care of by the state militias: the National Guard.
Only after a declaration of war was the President to get involved, and then only as an administrator; actual field decisions would of course be left to the commanders in the field. This is all in the Federalist Papers, in the numbers that deal with all these issues.
As for Obama holding back the Seals, I don't see it. My impression, and the impression of a lot of people by the way, is that he would have been attacked no matter what he did, for something. You guys had to come up with something to say, so you come up with him holding back the Seals. Given what actually happened, I don't think you're going to get much traction.
Going all the way back to the Phillipines, I don't see where FDR is complicit in what happened there. The Japanese struck very quickly, and had the element of surprise.
Your man Mitchell was drummed out in 1926 and he died in 1936, so once again, where FDR fits in, I have no idea. Your beef lies with Calvin Coolidge, who actively sought his court-martial. FDR doubtless could be fingered with making a bad decision in not bringing Mitchell back in, but I could easily envision the politics of that back then: it would have made FDR very unpopular with a large segment of the military establishment, who probably considered Mitchell a dangerous nut. So FDR was guilty of what many other Presidents have been guilty of before and since: believing too much in what their military "experts" have to say. But that's a very tough nut to crack, for anyone.
BTW, having read up on Mitchell and his report on how the Japanese would attack (
http://boards.history.com/topic/Pearl-Harbor-Forum/General-Billy-Mitchells/300032518) I have to say I'm seriously impressed. Too bad the folks back then didn't think so.