As Moshe and Yehoshua did before him, Yiftach tries to avoid war by sending a message to the enemy. The Children of Israel always offer their adversaries a choice between three options: make peace, flee the land, or fight. Although war is the least desirable choice, peace is not to be obtained at any price. In his message to the Ammonites, Yiftach emphasized that they were seeking to make war b’artzee (בארצי), meaning ‘on my country’ or, more literally, ‘in my land.’ Hashem has given the Land of Israel to the Children of Israel, and therefore their struggle to possess it is by divine right.
Source: Israel in the News