In the mid-19th century, Western powers began to infiltrate into Tibet under the guise of doing missionary work, exploring, and conducting business. While occupying the area, they left no stone unturned in seizing areas surrounding Tibet.

After the Opium War of 1840, the British imperialists launched a war of aggression against Tibet. Lhasa, as the capital of the region, bore the brunt. From that period on, the city lost the peace and stability it had enjoyed since the Middle Ages.

Britain invaded Tibet in 1888 and 1904. The Tibetan army and civilians resisted in Gampa, Gulho and Gyangze. Using rifles and guns, the British invaders seized Lhasa. When the local government of Tibet was being forced to sign the Treaty of Lhasa, the Qing court ordered High Commissioner Youtai not to sign it. During that same period, Tsarist Russia repeatedly sent special agents into Tibet. Russia also sent Buddhists to the three monasteries in Lhasa and the Tashilhungpo Monastery in Xigaze for "the study of Buddhist scriptures." Russian business people were sent to "conduct business'' in Lhasa and "Buddhist followers" were sent to worship holy sites in the city. All of these actions constituted major efforts of Russia to turn Tibet into a colony of the Russian Empire.

In 1906, Zhang Yingtang, an experienced diplomat and a reformist, was sent by the Qing court to Lhasa. He worked out 19 measures for the reform of politics and economics in Tibet, which were all adopted by the Qing emperor as new State policies for the governing of Tibet.

In the early 20th century, the 13th Dalai Lama, a few of his monks, and some lay officials visited China's hinterland and India. Enlightened by what he saw, the Dalai Lama developed ideas about improving management and introducing modern science and technology to Tibet. During this period, the local government of Tibet sent the children of noble families to study abroad. They returned to establish a power station, a bank, a post office, and a telegraph office in Lhasa. In the meantime, they worked hard to export sheep wool and cow tails. All of these developments helped boost urban construction in Lhasa and improve the lives of the Lhasans.

The feudal serf system, which had held sway in Tibet for hundreds of years, declined during that period, and Lhasa ceased to expand. Merciless political oppression, economic exploitation of serfs and slaves by serf-owners, usury, and natural disasters  deprived the Tibetans of the basic means of subsistence. Many serfs and slaves fled into Lhasa and lived on begging. As a result, there was a huge begging population in the city. Urban construction in Lhasa centered on monasteries and official residences, to the extent that there was no modern architecture or facilities for public service. The city did not have highways, rickshaws, or horse-drawn carts. All materials were transported to the city on the backs of men or animals. In the city, narrow streets were flanked by bare land and dilapidated housing. Without a water supply or sewage facilities, Lhasa was very muddy. Beggars were seen roaming around streets  that were dotted with rogues and dogs. Lhasa residents lived in an environment filled with poverty and backwardness, a situation which had to be ameliorated immediately.

On May 23, 1951, Tibet won peaceful liberation. Five-star red flags fluttered over Lhasa against the backdrop of blue sky. The ancient city finally entered a brand new era.