The role of a military – or, for that matter, any national security organ – is defense of the nation from threats. When the leadership of the security forces align themselves with one political party or faction, and in so doing abrogate their sworn responsibilities, they cease to be an element of the national defense, and become instead a security threat themselves.
A so-called national army that views itself as inextricably linked with only one segment of a society; with one political party to the exclusion of all others cannot by any stretch of the imagination be called a professional force. It is merely the armed wing of that party, and is less professional than most mercenary forces that at least fulfill the terms of their contract.
Military people are entitled to their personal political views, but those views should never be allowed to intrude on their duties. Soldiers are entitled to a vote, but not to force their views on the rest of the electorate, or to deny the electorate free expression of its views.
There are many forms of military dictatorship. There is the outright military coup, when the army overtly takes over the running of the state. As disgusting as this is, it at least has the decency of being out in the open. An even more insidious form of dictatorship, though, is when the military leadership uses coercion and threat to cow people into accepting its dictates; when it uses the implied threat of violence to force a country down a path other than the one its citizens would chose.
I spent 20 years as a professional soldier. I have some very definite political views, but never in my career did I allow those views to determine how I would carry out the duties I took an oath to perform. When the electorate spoke, I took seriously my oath to “protect and defend the Constitution.” If military officers around the world would take a step back and remember this, many of the world’s conflicts would be solved, and the earth would be a more peaceful place.