Bemidbar 27:21 says that prior to going to war, Yehoshu'a should stand before Elazar the Kohen and ask the Urim Vetumim questions, and go by its advice.
I am aware that there is a rule that no other prophet following Moses compared to Moses. Yet we do see that G-d Yehoshua does ask G-d questions such as after the initial defeat at 'Ai (Yehoshua ch. 7). Why did he have to use the Urim Vetumim regarding war-related questions rather than asking G-d directly? Is there something specific about preparing for war that requires using that medium?