Hi,
I have been reading a lot about the Song Dynasty recently, and I still do not understand one fundamental thing:
The Song dynasty was very wealthy, populous, it had an advanced economy, and some sources say that it (during certain periods) had an army of more than 1 million soldiers and around 85% of it's spending was on military.
So how was it possible that the Northern Song was conquered by the Jin Dynasty/the Jurchens?
I realise that Song China had much fewer horses than, say Tang China or the Jurchens, but still, with such a huge army and such financial resources, why couldn't it defend itself?
I also realise that the Song dynasty sought to prevent commanders from having too much power, so as not to go down the same path as the Tang did and that the Song government was bureaucratic and might have been inefficient in dealing with the Jurchens threat.
But still, nothing of this looks like a convincing explanation to me.
To me, it seems as strange as if today the United States would be conquered by Mexico. I can't make sense of how this could happen and none of the books I am reading provides a satisfying answer.
If you have an answer or a book recommendation (English or Chinese, though preferably English), it would be great!
It's a good question, and the answer isn't simple.
First, the Jin attacks in 1123-1126 and 1126-1127 caught the Song when they were relatively weak. The Song had engaged in aggressive war against Xi Xia (Tanguts) for much of the early 1100s, losing possibly many hundreds of thousands of soldiers, and spending very large sums of money of the effort, for very little gain. In addition to this, they also fought against the Liao (Khitans), with even less success (their allies, the Jin, were much more effective against the Liao).
The Song also faced major rebellions, especially in 1119-1121, most notably the Fang La rebellion. These rebellions appear to have, at least partly, resulted from economic pressure due to the expense of the war against Xi Xia. The Song lost control over large parts of their territory for months, millions died, and major military forces had to be diverted from the frontier wars to defeating the rebels (which is one reasons why Song forces performed poorly against the Liao).
Thus, in 1123-1127, Song finances were weak, not having recovered from their wars against Xi Xia and the Liao, nor from the rebellions, and their control over parts of their territory was shaky.
Second, while the Song had a very large army, which if concentrated could have easily crushed the attacking Jin forces, the army could not be so concentrated. The army had to control a large frontier and maintain internal order (especially in the wake of the rebellions of 1119-1121), and the forces that could be used to defend the capital (Kaifeng) were limited. Further, logistics prevented too large a part of the army being committed in one region for too long - armies need to be fed, and food supplies in an area will only support so many soldiers for so long.
Despite these problems, the Song did defend against the Jin attack of 1123-1126. While the Jin successfully broke through the border defences, they failed to quickly capture Taiyuan (the northern capital of the Song), and weren't able to combine their invading armies at Kaifeng, and the Song successfully defended Kaifeng. The successful defence of Kaifeng led to a peace treaty with the Jin, which was almost immediately broken (which led to the Jin attack of 1126-1127 and the fall of the Northern Song).
A key to the fighting was Taiyuan. Taiyuan held out until September 1126. The Song made multiple attempts to relieve Taiyuan during the 250 day siege. These attempts failed to save Taiyuan, and led to the destruction of the best of the remaining Song forces. As a result, the remaining Song forces available to defend Kaifeng in 1126-1127 were both smaller and of lower quality than the forces that had successfully defended Kaifeng in 1126. Worse, since Taiyuan had fallen, the Jin forces that had been committed to the siege of Taiyuan were now available for the second attack on Kaifeng. With the destruction of multiple Song armies in the 1123-1126 attack, and the continued fighting for Taiyuan, the Song had no forces left in the area which could stop the Jin in open battle - their only chance was to successfully defend Kaifeng. However, the defending forces were weak, and the attacking Jin forces were numerous, skilled, and well-led, and Kaifeng fell after a 3 week siege.
At this point, the Jin invasion of 1126-1127 was disastrous for the Song, but not necessarily fatal for the Northern Song. While the Jin were able to capture Kaifeng, they were not strong enough to take all the major cities, and the invasion could have ended as a devastating raid including the capture and sack of the northern capital Taiyuan and the main capital Kaifeng, followed by a peace treaty, rebuilding of the Song military, and eventual recovery of border areas ceded to the Jin. However, the capture of Kaifeng decapitated the Song government. The Song emperor had attempted to flee, but was captured by the Jin, and returned to Kaifeng. Only one of the emperor's sons had escaped capture (he had not been in Kaifeng); he was the emperor who restored Song rule in the south. With no effective Song government, there was no effective continuing defence of the north, and the north fell to the Jin.
A brief account of the catastrophe is given in the Cambridge History of China (chapter 7 in volume 5 part 1).
The problem of trying to defend northern China against a strong and mobile enemy was inherited by the Jin, with their new enemy being the Mongols. The Jin defence was much more effective that the Song defence - the Jin didn't have the equivalent of the unsuccessful and very costly wars the Song had in the first two decades of the 1100s, nor did they suffer the swift decapitation of their government that overtook the Song (but they did suffer from major rebellions, which contributed to their loss of control of Manchuria in the Jin-Mongol wars). The Jin defence against the Mongols shows what the Song might have been able to achieve, if they had pursued a sounder strategy.