Article 12 of the constitution of India defines the State. As per Art.12 State includes
The Union government and the Parliament of India .
The state government and the Legislature of each of the states.
All local or other authorities within the territory of India.
All local and other authorities under the control of the Government of India.
The term authority means a person or body exercising power to command (according to Webster’s Dictionary .) In the context of Art.12 the word authority means a body having the power to make laws, orders, bye-laws, regulations, notifications etc. These orders bye-laws and notifications have the effect of law and the said body also enjoys the power to enforce those laws.
Here Indian Army and so does the other military forces of our nation are directly under the control of the Union government of India. The President is the Chief Commanding officer of all armed forces in the country and these forces are directly controlled by the government through the defence ministry. Army has the power to make bye-laws and regulations to regulate their own internal affairs and they can issue orders and notifications to protect national security or the interst of the nation. Citizens have the duty to obey these orders and the military has the power to enforce those.
Hence the Indian Army along with other armed forces of the nation come under the defenition of state according to Art.12. The main objective of defining the state is to protect the bill of rights or as we call it the fundamental rights. The fundamental rights in part lll of the constitution is a guarantee of the state and we can sue the state if there is an infringement. We can sue only the state in case of an infringemenf of fundamental rights. So any action or inaction of any of the authorities as per Art.12 leads to a violation of any of the fundamental rights guranteed by the constitution we can sue the said authority and thus the State. We can directly approach the Supreme Court(Art.32) or High Courts (Art.226) in case of grieviences.