Step 1: Understanding the Concept:
The question asks to identify the major national movement that was launched with the Dandi March (also known as the Salt March).
Step 2: Detailed Explanation:
The Dandi March was a landmark event in the Indian independence movement. In March-April 1930, Mahatma Gandhi led a long march from his Sabarmati Ashram to the coastal village of Dandi. There, he broke the British Salt Law by producing salt from seawater. This symbolic act of defiance against British rule marked the beginning of the nationwide Civil Disobedience Movement. Millions of Indians across the country began to break the salt law and other unjust laws.
Step 3: Final Answer:
The Civil Disobedience Movement started with the Dandi March.