The Non-Cooperation programme was adopted by the Indian National Congress in 1920. It was a significant movement in the Indian independence struggle and marked a shift towards more assertive and active forms of resistance against British rule. The decision to adopt the Non-Cooperation programme was taken at the Nagpur session of the Congress in December 1920.

Background:
Prior to the Non-Cooperation movement, the Indian National Congress had been following a policy of constitutional agitation, seeking reforms and concessions from the British government. However, the frustration with the slow pace of reforms and the British response to the Jallianwala Bagh massacre in 1919 led to a growing radicalization among Indian leaders.

Key Principles of Non-Cooperation:
The Non-Cooperation programme was based on the principles of non-violence and non-cooperation with the British government. It aimed to mobilize the masses and create a mass movement against British rule. The key principles of the Non-Cooperation movement were:

1. Boycott of British goods: Indians were encouraged to boycott British goods and promote the use of Indian-made products. This was seen as a way to hit the British economically and promote Indian industries.

2. Non-cooperation with British institutions: Indians were urged to withdraw from British-run institutions, including schools, colleges, and law courts. This was aimed at undermining the legitimacy and authority of the British government.

3. Civil disobedience: Indians were encouraged to engage in acts of civil disobedience, including non-payment of taxes and non-compliance with British laws. This was seen as a way to challenge British authority and demonstrate Indian unity and resolve.

Impact and Significance:
The Non-Cooperation movement had a profound impact on the Indian independence struggle. It mobilized millions of people across India and brought them into the fold of the nationalist movement. It also marked a shift towards more assertive and active forms of resistance, challenging the legitimacy of British rule.

The movement saw widespread participation from various sections of society, including students, peasants, and workers. It helped in fostering a sense of national unity and solidarity among Indians, transcending regional and religious differences.

However, the movement was called off by Mahatma Gandhi in 1922 following the Chauri Chaura incident, where a group of protesters set fire to a police station, leading to the death of several policemen. Gandhi believed that the movement had lost its non-violent character and decided to suspend it.

Despite its premature end, the Non-Cooperation movement laid the foundation for future mass movements and inspired generations of Indians to actively participate in the struggle for independence. It demonstrated the power of non-violence and mass mobilization as effective tools against colonial rule.