Don’t forget one of the duties of the National Guard is to provide security and assistance during other sorts of emergencies than war, such as earthquakes or hurricaines or riots.
Yes, of course. In fact, males between 18 and 25 are required to register with the selective service, which is essentially the agency that would run a draft. But since the 1970’s the US has seen an all-volunteer force as desirable. Since the military spent much of the 80’s and 90’s encouraging folks to retire early and really, except in certain specialties, having more volunteers than job slots, it would be a little silly to bring back the draft at this point.
The National Guard is the state militia, of which we have 50. So… you have “National Guard of Illinois”, which is under control of the State of Illinois governor. If there’s a natural disaster in Illinois or some other emergency the NG of Illinois may be activated by the governor to maintain order, lend assistance to civilians, prevent looting, assist in evacuations, etc. During the 1960’s the various NG’s were used to control riots (with mixed success). After 9/11/01 extra airport security was provided by the various NG’s. So, in that sense, the NG is more oriented towards domestic defense, but NG units can and do fight abroad. Regular military - active duty and reservists - would likely only get involved in the event of fighting on American soil. The Federal military is prohibited by law from providing policing services (looting prevention, for example) on American territory - which is why it was the NG at the airports and not the Army or Marines.
See above. A very rough analogy would be comparing the armies of Germany or France with the NATO troops. Each State in the US has an army/air force/etc. controlled by the governor, it’s a State militia. Reservist would be a Federal military person. State militias can provide domestic policing services, Federal can not. Remember that many of the States in the US either started as separate and discreet colonies with a high degree of soverignity, or were actual separate nations (Texas, Hawaii) prior to joining the union. When Texas joined the Union, their national army became the Texas National Guard, or State militia.
All of this makes a military coup a little difficult to pull off. First of all, the Federal army knows they aren’t supposed to be soldiering on US soil. Even if the President (or some other official) convinced the Federal forces to follow him - which would violate everyone’s service oath* anyway - he’d be facing 50 State militias he’d have to convince to surrender or join up. As pilot141 pointed out, NG personnel may be more experienced than regular troops. They all have the same weapons. This could get really, really messy**
- US military personal do not swear an oath to an individual person or even a particular office - they swear to defend the Constitution. It’s an oath to uphold our framework of government and the rule of law, not a particular person, political party, or administration
** The U.S. Civil War was very nasty. More people died in the the Civil War than in all the other wars American has ever fought combined. During that war, we also invented the machine gun, landmine, trench warfare, concentration camps, and submarine warfare - and that’s just off the top of my head. Nobody wants to do that again.