Why did Indian troops enter Hyderabad in September 1948?

In September 1948, Indian troops entered the princely state of Hyderabad primarily because the ruling nizam refused to join the newly independent India, choosing instead to assert his autonomy.1

Tensions escalated significantly due to the actions of the Razakars, a Muslim militia that engaged in violence against Hindu communities. This instability and the nizam's continued efforts to maintain independence—despite a standstill agreement signed in 1947—prompted the Indian government to intervene. On September 13, 1948, the Indian army invaded the state, and within four days, the nizam’s forces were routed, leading to the state's accession to India.21