Why didn't the Tang Dynasty, with its powerful military strength, solve the Tubo problem?

Tubo is dominated by nomadic people, and its geographical conditions are easy to defend but difficult to attack. Therefore, even the Tang Dynasty with strong military strength could not cope with Tubo.

On the fighting capacity of the flat land, the Tang dynasty should have never been afraid of anyone, and basically never met an opponent. But if the battlefield is in Tubo, it will be difficult to fight, mainly for two reasons. First, Tubo is located on the Qinghai-Tibet Plateau in China, with a rather harsh climate and terrain. For Tang Jun, who is used to fighting in the plain, these two points are undoubtedly the most deadly. Before the start of the battle, the basic combat effectiveness was reduced by more than 70%. Second, the Tubo army is mostly a nomadic people, familiar with the terrain and used to the bad weather here. Their fighting capacity is naturally stronger than that of Tang Jun, and even if the number is not as good as that of Tang Jun, they can be outnumbered.

Another point is that the Tang Dynasty was in a period of prosperity, and its edge was too strong, so many neighboring countries refused to accept it. As a result, the Tang dynasty had to divide its forces to deal with other countries, and there was no way to deal with the more powerful Tubo. Moreover, the military policy of Tubo at that time was also very powerful. Without occupying an inch of land, they will recruit a large number of people from the local area, train them, train them into excellent soldiers and enrich their own army. And these people recruited from enemy-occupied areas are pioneers (that is, cannon fodder). Your own elite stayed at the end, giving the enemy a fatal blow.

To sum up, it is definitely impossible for the powerful Tang Dynasty to clean up Tubo, unless the Tang Dynasty raises the soldiers of the whole country, it is estimated that it is still possible. At that time, the emperor of the Tang Dynasty didn't do this. He adopted the method of kinship to ease the relationship. Princess Wencheng, a famous princess in history, married Tubo for the stability of the Tang Dynasty.