Under Article 355 of the Constitution of India, it is the duty of the

Under Article 355 of the Constitution of India, it is the duty of the Union to:

protect States against external aggression and internal disturbance
allow the extension of executive powers of the Union to any State
declare that the powers of the legislature of a State shall be exercisable by or under the authority of the Parliament
allow the Parliament to include or exclude any caste, race or tribe into the list of the Scheduled Castes or Scheduled Tribes
This question was previously asked in
UPSC CAPF – 2015
Under Article 355 of the Constitution of India, it is the duty of the Union to protect States against external aggression and internal disturbance.
Article 355 is part of the Emergency Provisions (Part XVIII) of the Indian Constitution. It explicitly states: “It shall be the duty of the Union to protect every State against external aggression and internal disturbance and to ensure that the government of every State is carried on in accordance with the provisions of this Constitution.”
This article forms the basis for the Union’s intervention in the affairs of a State in situations of emergency. Failure of a State government to function in accordance with the Constitution, as mentioned in Article 355, can lead to the imposition of President’s Rule under Article 356. The duty to protect against external aggression and internal disturbance is a fundamental aspect of the federal structure, ensuring the integrity and stability of the country.