No, I'm thinking of the Pentagon. Have you read the Constitution? I don't see anything in there about the military being assembled to accomplish the President's political goals. Where are you getting your information?
Basic military theory and philosophy, really, going back to Carl von Clausewitz: "War is merely the continuation of politics with other means." Still studied at military academies in many countries... including this one.
There's a reason, after all, that the President, while "Commander-in-Chief" of the armed forces, is still considered a
civilian.
Also a fair-to-middlin' understanding of US history and legal precedent helps here. Now, I did err by omission when I said that the military is a tool to enforce politics, because I
should have specified a tool to enforce
foreign policy only, as the Posse Comitamus act of 1878 (signed by President Rutherford B. Hayes) severely limits the use of the military to enforce
domestic policy.
...and as I mentioned, immigration enforcement is a
domestic policy issue, which is why the Customs and Border Patrol reports to the Department of Homeland Security -- a civilian branch of the President's Cabinet, and
not to the Pentagon.
It's all common sense, really. Let's say, for example, that a foreign government -- oh, I don't know, Madagascar -- is doing something we'd prefer they weren't, and we want to convince them to stop.
Our President's options can be easily broken down in three categories:
1. Diplomatic: go to the UN; condemn Madagascar.
2. Economic: go to Congress; impose sanctions against Madagascar.
3. Military: go to the Pentagon; authorize "Operation Bomb Madagascar Back to the Stone Age."
Obviously this is a gross oversimplification, but you get the idea. The point is that if, instead of Madagascar, it was, let's say, South Dakota doing something naughty, option 3 is
absolutely off the table... and if you think about it, you'll see why this must be so.
You
do not want a president who can use the military to enforce his will within these borders.