How to understand Lenin's slogan of "turning the imperialist war into a civil war" and explain it in detail! thank you

The imperialist war was the first world war, and Russia participated in the war as an allied group. However, the reform of serfdom in Russia in 186 1 retained a lot of feudal colors, and capitalism was not fully developed. World War I aroused the inherent contradictions in Russia, and the people's lives were miserable, even the frontline soldiers were very miserable. Therefore, Lenin suggested launching a revolutionary war to overthrow Russia's autocratic rule and establish the proletariat.