Answer by taking a quote from the following article:

Kisan Baburao Hazare was born on 15 June 1937 (some sources say 15 January 1940) in Bhingar, near Ahmednagar. He was the eldest son of Baburao Hazare and Laxmi Bai. He has two sisters and four brothers. He later adopted the name Anna, which in Marathi means "elder person" or "father".

Hazare was drafted in the Indian Army in April 1960, where he initially worked as an army truck driver and was later attested as a soldier. He undertook army training at Aurangabad.  During the Indo-Pakistani War of 1965, Hazare was posted at the border in the Khem Karan sector. He was the sole survivor of an enemy attack--variously claimed to have been a bomb, an aerial assault and an exchange of fire at the border--while he was driving a truck. The experiences of wartime, coupled with the poverty from which he had come, affected him. He considered suicide at one point but turned instead to pondering the meaning of life and death. He said of the truck attack, "[It] sent me thinking. I felt that God wanted me to stay alive for some reason. I was reborn in the battlefield of Khem Karan. And I decided to dedicate my new life to serving people." At a book stand in New Delhi railway station, he came across Swami Vivekananda's booklet "Call to the youth for nation building" which inspired him to think deeper. He spent his spare time reading the works of Swami Vivekananda, Gandhi, and Vinoba Bhave. In a blog post, Hazare expressed his views on Kashmir by saying that it was his "active conviction that Kashmir is an integral part of India" and that if required once again for service, he would remain "ready to take part in war against Pakistan."  During his fifteen-year career in the army (1960-75), Anna Hazare was posted at several locations, including Punjab (Indo Pak war 1965), Nagaland, Bombay (1971) and Jammu (1974)  During the Indo pak war, Hazare survived a road crash while driving for the army. He interpreted his survival as a further sign that his life was intended to be dedicated to service. He had another escape in Nagaland, where one night, underground Naga rebels attacked his post and killed all the inmates. He had a miraculous escape as he had gone out to return nature's call and hence turned out to be the lone survivor.  Official records show that he was honourably discharged in 1975 after completing 12 years of service.

What was his position in the army?
he initially worked as an army truck driver and was later attested as a soldier.