The day is significant because on October 27, 1947, the first troops of the Indian Army landed at Srinagar airport, forcing the invaders, backed by Pakistan, to retreat.
Source: Indian Army - X
On October 26, 1947, the Maharaja of Jammu and Kashmir, Hari Singh, signed the instrument of accession, and the princely state became a part of the Indian Union
Source: Indian Army - X
A Battalion of the Sikh Regiment reached the Srinagar air base to fight against the tribal invaders, who were backed by Pakistan