Why did Panos Kammenos and the Independent Greeks leave Alexis Tsipras's coalition government in 2019?

Panos Kammenos and his party, the Independent Greeks, withdrew from the coalition government led by Alexis Tsipras in January 2019 in protest of the Prespa Agreement.1

This agreement, reached in 2018, aimed to resolve a long-standing dispute regarding the name of North Macedonia. Under the terms of the deal, the country would be officially recognized as the Republic of North Macedonia, a change that required constitutional amendments in North Macedonia and subsequent approval by the Greek parliament.1

Kammenos, who served as defense minister, strongly opposed the agreement. His resignation and the party's departure from the coalition eliminated Tsipras's parliamentary majority, forcing the prime minister to call for a vote of confidence, which he narrowly survived before the agreement was ultimately approved by parliament.1