Final answer:
Mercy Otis Warren's main contribution to the war was writing influential pamphlets that supported the patriot cause.
Step-by-step explanation:
Mercy Otis Warren's main contribution to the war was writing influential pamphlets that supported the patriot cause. She actively opposed British reform measures before the outbreak of fighting in 1775 by publishing anti-British works. In 1812, she published a three-volume history of the Revolution.
By publishing her work, Warren stepped out of the female sphere and into the otherwise male-dominated sphere of public life.