Who are the four hoursemen in dürers print ?

The horsemen. In the text of Revelation, the main distinguishing feature of the four horses is their color; white for conquest, red for war, black for pestilence and/or famine, and pale (from 'pallor') for death (Clint Eastwood, Pale Rider, anyone?).

Explanation:

answer; taking up arms to defend the nation;