'To take up the hatchet' definitions:

Definition of 'To take up the hatchet'

From: GCIDE

Hatchet \Hatch"et\ (-[e^]t), n. [F. hachette, dim. of hache ax. See 1st Hatch, Hash.]
1. A small ax with a short handle, to be used with one hand. [1913 Webster]
2. Specifically, a tomahawk. [1913 Webster]
Buried was the bloody hatchet. --Longfellow. [1913 Webster]
hatchet face, a thin, sharp face, like the edge of a hatchet; hence:
hatchet-faced, sharp-visaged. --Dryden.
To bury the hatchet, to make peace or become reconciled.
To take up the hatchet, to make or declare war. The last two phrases are derived from the practice of the American Indians.