The bitter confrontations between proslavery and antislavery factions earned the new kansas territory the name
kansas hawks
free soldiers
bleeding kansas

The best answer is bleeding Kansas.

Bleeding Kansas was the name given to a series of violent confrontations in Kansas, and the neighboring border towns of Missouri, following the passing of the 1854 Kansa - Nebraska Act. The conflicts between Anti - slavery and Pro - slavery militant activists from 1854 - 1861 that reached  a state of low intensity civil war.

The border war known as Bleeding Kansas  was a crucial point that led to the road of the American civil war of 1861 - 1865. The outbreak of the violent event in Kansas came during the presidency of Franklin Pierce,

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