The Potala Palace is said to have been built in the 7th century for Princess Wencheng, a very famous princess in history of China. It was King Songtsan Gambo who had made the Potala Palace built. It was said that he had been a wise, handsome and brave man, with a strong body, a charming figure and heavy features.
In 629, the third year of Emperor Li Shimin's reign, a coup d'etat took place in Tubo. Its 31st tsampo, or King, was assassinated by his political opponent. The kingdom was seized with a movement of separatism championed by the aristocrats bent on returning to the old system. Songtsan Gambo became the 32nd tsampo. Though he was only thirteen at the time, he had already been a resourceful statesman. Calmly exploiting his diplomatic and military clout, he crushed the separatist movement, and in three years Tubo became an integrated kingdom again. Then he crossed the Yalutsangbo River and established the capital at Lhasa. Songtsan Gambo has since become a national hero of the Tibetans and worshiped like the revered Lamas.
After the reunification, Songtsan Gambo concentrated on building Tubo into a powerful kingdom. One of his nation-building strategies was to inject new cultures into Tubo. To do so, he found it the most convenient way to establish matrimonial relationships between his royal family and those of his neighboring countries. After marrying a princess of Nepal, he turned his attention to Tang. A hero himself, he admired Emperor Taizong of Tang for his great talent and bold vision. He thought he, as well as his kingdom, could gain a lot by his marriage with a daughter of the Tang emperor.
In 634, Songtsan Gambo dispatched an envoy named Gar Tongtsan to Chang'an, capital of the Tang Empire, to find out whether there was a chance for the Emperor Taizong of Tang to marry off one of his daughters to him. But the Emperor refused his proposal considering the political and military reasons and his state of marriage.
As king of Tubo, Songtsan Gambo had married three Tibetan girls and the Nepalese princess Khir-btsun before he made his marriage proposal to Tang Dynasty. None of the three Tibetan wives was given the title of Queen but the Nepalese Princess, who was the daughter of Amsuvarman (king of Nepal).
Of course the political and military reasons were most likely the main obstacles that Emperor Taizong turned down Songtsan Gambo’s marriage proposal. The historical record tells that it was because of the King of another country who had said something bad of Songtsan Gambo to Emperor Taizong. Hearing of the envoy’s report, Songtsan Gambo got very angry and decided to fight for his country and for his own sake. Successfully, he defeated the country whose king had prevented him from marrying a princess of Tang emperor in a short time. Then, to show Tubo’s great military power to Emperor Taizong of Tang, and to extend territory of his country, Songtsan Gambo had continuously launched offensives against his neighboring countries and won great victories until his successes threatened to the security of the Central Plains. Realizing that he should take the talented young man seriously, Emperor Taizong led an army troop of 50.000 soldiers personally against Songtsan Gambo’s 20.000 soldiers and defeated them.
Still wishing that he could marry a princess of imperial Tang, and the Princess would introduce the advanced culture and production technologies from the Central Plains to strengthen Tubo, Songtsan Gambo sent his Prime Minister Lu Tongtsan to Chang’an to officially propose the matrimonial relationship to Emperor Taizong. Songtsan Gambo trusted Lu Tongtsan not only because he was a resourceful military leader who had played a great role in the reunification of Tubo, but also because he was a steadfast champion of his policy to establish friendly relationships with neighboring countries.
It was a wintry day. Lu Tongtsan and his hundred-strong entourage arrived in Chang'an with 5,000 taels of gold and several hundred items of treasure. Emperor Taizong of Tang received them in his richly ornamented palace. There, Lu Tongtsan presented Songtsan Gambo’s letter of proposal along with the gifts. Though impressed with Lu Tongtsan’s elegant manner, Emperor Taizong refrained from acceding to Songtsan Gambo's proposal right away. He put Lu Tongtsan and his men up in the royal hotel together with a dozen envoys and their subordinates who had come for the same purposes from other countries. The emperor needed to find a tactical way to decline them so that he could marry the princess off to Lu Tongtsan's monarch Songtsan Gambo. Having a contest among them seemed to be a good idea.
Even though Emperor Taizong had anticipated who the winner would be, he was still amazed at Lu Tongtsan's intelligence. In 641, Emperor Taizong betrothed Princess Wencheng to Songtsan Gambo and granted the title of "Right-Wing General" to the Tubo envoy Lu Tongtsan, making him the first Tubo man to receive an honorific title from the central government. Later, Princess Jincheng was married off in Tubo. Since then, the Tubo Kingdom established "uncle-nephew" relations with the Tang Dynasty, which were accepted by tsampos of future generations.