Tensions steadily increased between the two nations when Mao implied that the Lhasa rebellion in Tibet was caused by Indians. On 6 May 1959, Mao published "The Revolution in Tibet and Nehru's Philosophy" where he accused Nehru of openly encouraging Tibetan rebels. This publication was evident of China's perception of India as a threat to its rule of Tibet, which became an underlying reason for triggering the Sino-Indian War. India had become the imperialist enemy, with Nehru and his "big bourgeoisie" striving to "prevent China from exercising full sovereignty over its territory of Tibet" to form of a buffer zone. On the same day, Zhou Enlai lashed out at Nehru's "class nature".