Who was the person that Leon Trotsky worked with closely after the revolution?

After the Russian Revolution, Leon Trotsky worked closely with Vladimir Lenin. As a key leader in the Bolshevik Party, Trotsky played a significant role in the October Revolution and later served as the People's Commissar for Foreign Affairs and the founder of the Red Army. Their collaboration was pivotal in consolidating Bolshevik power during the early years of Soviet Russia. However, their relationship became strained after Lenin's death, leading to Trotsky's eventual opposition to Joseph Stalin.