If we use World War Two as a model for World War Three one thing becomes immediately apparent. World War Three will likely not involve a land war in Asia of the west attacking east, or a land war in Europe of east attacking west. I know this conclusion seems counter productive given that both World War One and Two were precisely fought in those arenas, but bear with me.
Everyone’s military is smaller now. Even China, with the largest military force by numbers, is smaller than the Soviet total military at the start of Operation Barbarosa. At that time the Soviets had 14 million in Reserve forces alone, which allowed them to generate Divisions just as fast as the Wehrmacht whittled them away to the tune of over 27,000 persons per day. The Germans were being whittled at about a tenth of that, but given their smaller starting numbers, in the end Stalin’s observation that “quantity has a quality all its own” proved true. At least it proved true with western logistical support for trucks, ammo, weapons, etc.
Because everyone’s military forces are smaller (both active and reserve) Word War Three is limited to some form of nuclear missile exchange (aka the great fear of the last Cold War) or some form of direct conflict not in Europe or Asia which will devolve into a stalemate as did Korea. I like to think that this is the same sort of outcome as the 1973 Arab Israeli conflict, where both sides fought to a political standstill as the Americans rapidly reinforced the Israelis and the Soviets did their best for their Muslim allies. But that war ate up more than a years worth of economic output from either the Soviets or Americans, so it showed exactly how costly a peer to peer fight is.
So…the Americans chose to develop better fighting systems so it wouldn’t be a true peer fight. And the Soviets chose to develop extensive electronic warfare capabilities to nullify the American (aka western) ability to sense and communicate so that they could use their superior numbers to overwhelm the west at points (a technique they perfected in The Great Patriotic War as they fought from Moscow to Berlin). In short, the Americans planned on winning in open warfare by being better on the field in terms of combined arms maneuver, and the Soviets planned on winning in open warfare by setting the conditions to rely on defense until they could mass overwhelming firepower combined with surprise and information isolation of their opponent.
Desert Storm, unfortunately does NOT give us good information on what an American versus Russian or American versus Chinese conflict would look like. Each of those three nations has a distinct “character” about how they wage war and advance their national interests. Both Russia and China are willing to take a longer time-frame to advance their interests before committing military forces, which makes it difficult to predict WHEN they would commit forces.
So…why do I think that World War Three won’t be a land war? The occupation attempts of Afghanistan by the Soviets, then Americans. The “insurgency” in Iraq. The modern lessons that a conquered people are not truly conquered, especially not in an area as heavily armed as the United States. Ground warfare to impose political change on another country has prove quite foolhardy to both the east and west. The classical “war is a contest to impose your will on the opponent” has pretty much been broken as a model for post WWII warfare.
So what will World War Three look like? A few scenarios come to mind, such the military invasion of Taiwan that triggers a US response that drags Russia into the mix could do it. Alternately North Korea truly going rogue, launching a high altitude EMP nuke at the US over the polar shot, and invading south could do it as that pulls in all the major players too. Less likely, Russia fakes a “spontaneous referendum” in the territory of a NATO member and triggers and Article 5 response. Or Russia blunders into a fighting war by making a critical mistake with an aggressive unannounced flyby or sailby that causes an accident and suddenly we are all in a shooting war at sea.
Even darker possibilities for World War Three exist. Biological warfare for example, could potentially eliminate enough of a target population that classical “invade and conquer” tactics might tempt leaders into using them. The Soviets had a pretty robust biological warfare research program, and good money would bet on the Chinese having at least a few illegal research sights on the mainland.
Of course my crystal ball works about as well as any hucksters, so I have no clue if my thoughts on the matter have any bearing on our actual future. Honestly the status quo of proxy wars and economic tit for tat sparring is the most likely future for all the great powers.