During July of 1917, demonstrators in Petrograd (including sailors from Kronstadt) were met with fierce opposition by soldiers of the provisional government. The former minister of war, Alexander Kerensky, was appointed prime minister. His power base, however, was weak and the army did not trust him.
Forced to turn to the soviets for help in preventing another revolution, Kerensky made a deal with his erstwhile enemies. A July revolution was effectively stopped, but now members of the soviets were armed. They would not give up their weapons easily.
The Bolsheviks still had a chance to violently overthrow the government, although Lenin believed any chance of total revolution had ended when the government stopped the July uprising. Sensing the time was finally right, in October of 1917, Lenin returned to Petrograd from his hideaway in Finland. He immediately began to agitate for armed revolution.
He received an unexpected gift. That month, many of the Bolshevik leaders (who had been arrested during the July uprising) were let out of jail. The provisional government could not have made a worse mistake.
Because Lenin believed the new Russian government had to be forcefully overthrown, in a Bolshevik Revolution, he sought a wide base of help. On the 24th of October, the Bolsheviks formally asked the Kronstadt sailors to participate in their endeavor. Believing they were aiding the soviets, the sailors agreed. Their differences with Lenin would have to be sorted-out later.
Thinking about their best strategy, Lenin and his Bolsheviks made a plan to topple the government. Among other things, they would seize the Winter Palace, a significant symbol of Tsarist power.
Credits
From Russian Revolution: Freedom and Hope, a BBC documentary