Original: From 1947 to 1948 , soon after the Partition of India and of the Indian Army , the two new armies fought each other in the First Kashmir War , beginning a bitter rivalry which has continued into the 21st century .
Simplified: Soon after the Partition of India , both the newly formed armies fought each other in the First Kashmir War from 1947 - '48 which begun the bitter rivalry that has continued into the 21st century .