Assertion: The Maharaja of Kashmir signed the instrument of accession in October 1947.
Reason: Some Pakistani infiltrators invaded Kashmir in October 1947. India extended military support to Kashmir and drove back the infiltrators.

Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

In October 1947, Pakistan sent tribal infiltrators from its side to capture Kashmir. This forced the Maharaja to ask for Indian military help. India extended the military support and drove back the infiltrators from Kashmir valley, but only after the Maharaja had signed an ‘Instrument of Accession’ with the Government of India. However, as Pakistan continued to control a sizeable part of the state, the issue was taken to the Union Nations Organisation, which in its resolution dated 21 April 1948 recommended a three-step process to resolve the issue.

Since then the politics of Jammu and Kashmir remained controversial and conflict-ridden both for external and internal reasons. Externally, Pakistan has always claimed that Kashmir valley should be part of Pakistan. Pakistan sponsored a tribal invasion of the State in 1947, as a consequence of which one part of the State came under Pakistani control. India claims that this area is under illegal occupation. Pakistan describes this area as ‘Azad Pakistan’. Ever since 1947, Kashmir has remained a major issue of conflict between India and Pakistan.