Cold War Etiquette between the U.S. and Russia

The U.S. stayed out (mostly) of Afghanistan when the Soviet Union was there during the 1980s.

The Russians (mostly) mostly stayed out of the Viet Nam War while that was going on.

Russia (mostly) stayed out of Afghanistan while the U.S. went in after Osama Bin Laden.

Russia mostly stayed out of Iraq between 2003 and 2011 or so when we left there.

This is the Nuclear Detente Cold War Etiquette as played by the Soviet Union and the U.S.

However, now things are different in regard to the Middle East and Russia and the U.S. to some degree.

The U.S. (because of Russia's presence as Russia and before that the Soviet Union has had a relationship with Syria and Iran since at least 1980 or sooner. So, generally, the U.S. has stayed back from getting too involved in Syria or Iran's business because of nuclear Detente.

People think Obama didn't send troops into Syria because he didn't know what he was doing.

NO.  That wasn't it. He was using tried and true methods of preventing a nuclear war that has been used successfully with the Soviet Union and now Russia and by the U.S. since the end of World War II.

However, now there is a problem. Because Russia is building up troops and equipment once again in Syria it is upsetting many nations in the Middle East and around the world.

However, my belief is that unless there was some kind of gentleman's agreement about Russia doing this with both NATO and the U.S. secretly that Russia wouldn't go into Syria again with a lot of weapons. However, I might be wrong about this.

So, we might, for example, see Russia totally wipe out ISIS. We might see him just defend Assad from being overthrown. We might see any or all of these things or more at this point.

The fact that Sunni nations are worried about the Russian military buildup in Syria shouldn't come as a surprise to anyone. I wouldn't be surprised for example if Russia swept across Syria and Iraq and wiped out ISIS at this point.

Whatever Russia does it might do as a Blitzkrieg all at once as this is Putin's style like it was Hitler's too. So, if and when Russian Armor moves it likely will mow down every man, woman and child in it's way. So, likely a lot of innocent people will die along with ISIS.

Note added September 24th 2015:

The Russian Army is known for it's brutality in quick actions. It is more like this than any other Huge army on earth. In fact, I can think of no large army on earth better suited to take out ISIS (along with anyone alive in ISIS areas). They are the only international large army that could get away with this, and I think that the rest of the large countries on earth secretly agree with doing this and might even secretly finance Russia's actions. A new kind of detente between Russia and the western world secretly might have emerged. This is one good possibility. However, if and when Russia wipes out ISIS the world will mightily complain publicly because of the amount of people and infrastructure in Syria and Iraq that will be wiped from the map. This is one possibility. However, the way things are presently progressing this becomes more and more likely as a way for the world to rid itself of ISIS through technological blitzkrieg warfare in the extreme.