What does Judges 11:19 mean?

'Israel sent messengers to Sihon, king of the Amorites at Heshbon, asking to pass through his land. But Sihon didn't trust Israel and gathered his army at Jahaz to fight them.' Judges 11:19 - Modern Text Bible

(Jephthah points out that the only reason Israel fought was because Sihon attacked them first.)