What kind of work do computer engineers do in the Indian Army? What is their role in war-field postings?

Army is a common ground if recruited under certain categories. A basic degree is all that takes for a person of Indian nationality to get into the armed forces. So you're a training cadet or a ranking officer in the army, irrespective of your feild of specialisation in engineering. But your feild is really important when you want to get into navy or air force. They check your technical skills. It's highy not recommended for mechanical or civil engineers to join the air force as a pilot. But with the same, take up a technical duty. You're in for a treat. You'll be taking care of the fleet under maintainance if you're very good at your basics and skills. The navy guys who've majored in electronics and co. or instrumentation enjoy privileges. So everything depends on what wing in  the armed forces you want to join. Army is the most promising place but you'll be there for a very short time*. *for a very short time: Once you're a ranking officer, you are expected to take up exams competing for higher posts. There would be thousands of officers writing alongside you. The filtration takes place for 10 in 500, 2 in 50, 1 in 10 etc. So if you fail to clear in three attempts, you are done for good.