First, the purpose of overreaching Tibetans and relatives is to maintain friendly exchanges between the two countries. At that time, the core policy was that one side was strong and the other was weak, and affinity was used to maintain the balance between the two. The focus is on Tubo at that time. It's so arrogant that I think I'm awesome, so I want to attack the Tang Empire. Especially at that time, Songzan Gambu thought he was very powerful and wanted to marry the daughter of Emperor Taizong. Tubo is a remote and poor place, and Emperor Taizong is naturally unwilling. As a result, Tubo actually wanted to fight the Tang Dynasty, and without any accident, he lost immediately.
Second, the Tang Dynasty won the war, but wanted the title, so it agreed to the request of Tubo. Although the Tang Dynasty won the war, it also suppressed the momentum of Tubo. However, China people have always advocated peace, and the Tang Dynasty wanted to show its generosity, so they agreed to get married, but instead of their own daughter, they sent a princess selected from the imperial clan. At that time, Tubo thought he had married the princess, but he was really happy.
Third, Princess Wencheng asked Tubo by going up one flight of stairs. In fact, this move in the Tang Dynasty just wanted to make other people feel generous, and they didn't want to bring any substantial help to Tubo, because they felt that they were just sending a woman. But I didn't expect Princess Wencheng to be a treasure, which brought rapid development to Tubo's economy and crops, and even introduced advanced culture, and Tubo found a treasure.