Why Putin's sudden pullout from Syria?
There are several reasons offered here but nobody but Putin himself really knows.
It seems to me that the biggest mystery was its suddenness. None of the proffered explanations really explain that. I think it can be explained from a military perspective, however. But to offer that explanation, I have to expound the concept of an "industrial base". And I think I can do that best by going back to WWII. I think the concept explains the outcome of WWII, in fact.
When WWII started, Britain was a major industrial power. Its innumerable factories churned out goods that were exported around the world. The days when Britain was the workshop of the world were gone but it was still a pretty big workshop. And of particular relevance, it manufactured and exported lots of motor vehicles. It still does but the nameplates on them these days are Nissan, Honda and Toyota, not Austin, Morris and Leyland.
And the aircraft of the day and the motor vehicles of the day had a lot in common. They both used piston engines, for instance. So when the war broke out the production of civilian motor vehicles was stopped and the factories were converted to make military aircraft. And the resultant productivity from all those factories was huge.
The experienced fighter pilots of the Luftwaffe sat in planes armed with cannon while the Hurricanes and Spitfires of the RAF were armed with machine guns only. Aircraft of the day could take quite a lot of damage from machine guns and still keep flying. But a cannon hit was mostly curtains. So the Luftwaffe pilots in their ME 109s made mincemeat of the poorly trained pilots of the RAF. The kill ratio was vastly in favour of the Luftwaffe.
Yet whenever a fleet of German bombers came over Britain with their Messerschmitt escorts, a flight of RAF fighters rose up to oppose them. How come? How come there were any RAF planes still flying after so many had been shot down? The answer: Britain's industrial base. Britain could build fighter aircraft as fast as the Luftwaffe could shoot them down.
The bombers still mostly got through -- witness the devastation of places like Coventry and London -- but there were of course some losses and it became clear to the Oberkommando der Wehrmacht that they could use their planes to better effect elsewhere -- particularly in Russia, where it was in fact something of a turkey shoot for the Luftwaffe. So they ceased their campaign against Britain.
Mr Putin is not in anything like the WWII British position. Russia has quite a small industrial base. It is still mainly a primary-producing country. The Soviets knew that of course so over many years they laboriously built up an economy within an economy. They built up a vast complex of factories and maintenance facilities that was permanently devoted to military production and maintenance. So they could afford a war. They could to some extent replace losses in battle.
Even so, however, they did not rely on that. One of the interesting things revealed when West Germany took over East Germany was the very large stocks of all military materials that the East had built up. They had in stock as much as ten times as many bullets, shells etc as the West did. They were not confident that they could produce enough in a war to keep the troops supplied. And since their military was closely integrated with Russia's, there is little doubt that Russia had adopted similar measures.
But when Gorbachev became President of the Soviet Union he was horrified by how much the military establishment was draining out of the overall Soviet economy -- and it seems likely that he immediately started to put the brakes on the military economy. And when he fell in 1991, the military economy was virtually abandoned. Not only were Russia's ships, submarines and aircraft left to rust but the factories that produced them and the facilities used to maintain them were also left to rust.
So when Vladimir Vladimirovich Putin came to power in 2000, that decay had largely neutered Russia's armed forces. And a lot of the decay remains unremedied to this day. Most of the navy is still rusting in port and when Russian aircraft carrier Admiral Kuznetsov puts to sea it has to be accompanied by tugs in case it breaks down.
But Putin has slowly renovated enough of his forces to support limited interventions -- as in Georgia and Syria. But with the loss of the Soviet war economy he is up against Russia's limited industrial base. He has used up a lot of the bombs and missiles that he had stockpiled and reached a point beyond which he dare not go. He cannot soon replace the bombs and missiles he has used so runs the risk of Russia being unable to defend itself if he runs his stocks down any further. He has hit a red line in his stocks of war materiel. And when he saw that such a point had been reached, he immediately pulled the plug on his war in Syria.
So I think the suddenness of the pullout was motivated by a sudden realization of how far he had run down his stocks of war materiel. I was actually waiting for that to happen because it was clear that Russia was using up a lot of bombs and missiles that it could not rapidly replace.
UPDATE: Two more thoughts about industrial bases.
With the vast U.S. industrial base and large population, both Germany and Japan were doomed as soon as the U.S. entered WWII. That was most vivid when the allies started bombing Germany. The heavily armed ME110 night-fighters and the skilled German anti-aircraft gunners were very good at knocking allied bombers down. The average life of a bomber was about 4 sorties. An uncle of mine died in one. But great waves of bombers just kept coming. Civilian motor vehicle production had been converted into military aircraft production in the USA too. Japan's Admiral Yamamoto actually foresaw that Japan could not compete with America's industrial base and large population when he opposed the strike on Pearl Harbour.
In the 21st century the world once again has a country that is the workshop of the world: China. So combine that huge industrial base with China's almost limitless manpower and it becomes clear that China could not now be opposed in a conventional war. The war would have to go nuclear almost immediately.