Why did India extend military support to Kashmir in October 1947?

To counter the tribal infiltrators sent by Pakistan

India provided military support to repel the tribal infiltrators sent by Pakistan to capture Kashmir.

The period following India's independence saw significant political developments. In October 1947, Pakistan dispatched tribal infiltrators to capture Kashmir, prompting the Maharaja to seek Indian military assistance. Subsequently, India provided military support to repel the infiltrators from the Kashmir valley. This intervention occurred subsequent to the Maharaja's endorsement of an 'Instrument of Accession' with the Government of India.