Both Lenin and Trotsky had assumed that the Bolshevik seizure of power would spark similar revolutions elsewhere in Europe n.b Germany, which seemed ripe for revolution by all the economic, social and political criteria put forward by Marx.
But the Bolsheviks were simultaneously committed to pursuing peace with that government. This was despite knowing that peace would strengthen the Imperial government they wished to destroy.
Trotsky began peace negotiations in December 1917. The German Imperialist government demanded, as its price, large swathes of Russian territory.
This split the Bolsheviks, with Nikolai Bukharin leading the 'revolutionary war group'. Protracted arguments followed in which practical necessity and the need for unity triumphed over pure ideology.
Trotsky's solution was 'neither peace nor war' - retreating further if necessary while awaiting the revolution in the West.
However Lenin took a more pragmatic view and argued for the acceptance of the German terms. After a long debate, the Treaty of Brest-Litovsk was signed in 1918. However, this was only after Lenin twice offered to resign.
This decision was important for the future direction of the Soviet state. It set a precedent for future action by establishing that 'socialism at home' would take priority over the spread of international revolution. This commitment provided the intellectual foundation for Stalin's later 'Soviet-first' approach.