How did Hari Singh’s accession of Jammu and Kashmir to India lead to war with Pakistan?

Following the 1947 partition of the Indian subcontinent, the ruler of the princely state of Jammu and Kashmir, Hari Singh, initially sought to maintain the region's independence. However, his position became untenable following a revolution among his Muslim subjects and an invasion by Pashtun tribesmen from Pakistan.123

To secure military assistance against these forces, Hari Singh signed the Instrument of Accession in October 1947, formally joining the state to the Indian union. This act triggered immediate conflict: India moved to defend and confirm the legal accession, while Pakistan—viewing the Muslim-majority region as a natural extension of its own territory—intervened militarily.321

This confrontation resulted in the first war between the two nations, which continued until a United Nations-brokered ceasefire took effect in January 1949. The conflict ultimately led to the establishment of a ceasefire line, later known as the line of control, which continues to divide the administration of the region today.124