What was the main reason for russian expansionism in the 1800s?

The main reason for Russian expansion in 1800s was the end and attempt to gain a warm-water port.

By the 1800s, Russia was already one the largest Empires in the world. It had large swathes of land in Europe and Asia and had tremendous natural resources in terms of timber, fresh water, minerals etc.

However, despite it's immense size Russia lacked a warm-water port. Both it's ports in the Pacific and the north Atlantic were closed every year due to ice.

This several restricted Russia's trading prospects and posed a natural security threat in terms of a blockade.

Within a few years, Russia was able to acquire a port in the Black Sea in Crimea.

alliances in ww1 were different from ww2 because the entente in ww1 made up of serbia,russia,france,britan,japan and italy later america  and all allied in a sort of balance of power and too keep germany,austria-hungary,and the ottomans down. russia allied the serbians in order to exert its influence in the balkans while france allied the russians because france was still in dismay and insulted after the defeat to the germans during the unification of germany and britian allied the belgians after the germans invasion of belgium.in ww2 the alliances were in a preemptive attempt to deter any further wars into happening while germany and italy allied since they were insulted and humiliated after the previous war while also sharing a similar ideology of facsim along with japan which all 3 had a want for world domination and agreed to assist one another in the endevours 

explanation:

a plantation economy is an economy based on agricultural mass production, usually of a few commodity crops grown on large farms called plantations. plantation economies rely on the export of cash crops as a source of income.

i hope this : )