Which of the following objectives proved to be the hardest and took the longest to accomplish?

I believe it is the taking of Richmond that took the longest and was the hardest.

Explanation: Many soldiers on both sides lost their lives over four years of campaigning.

1) the taiping rebellion was prompted from 1850-1864 and waged against the ruling of machu qing dynasty. the rebellion was caused by hong xiuquan and class differences, later leading to a radical change in social and economic structure.

3) karl marx, a believer of the principle of socialism, believed that the working class would have to free themselves from the exploitation of industrialists by establishing a radical socialist classless society where all industries and   property are owned by the state.

5) as indians revolt gained power, people found additional reasons to protest against the british rule. princely families joined the uprising due to changes to the inheritance law which made adopted children ineligible to assume the throne. this was an attempt by the british to control royal succession in the princely states that were nominally independent from the british.