C. F. Keil and Franz Delitzsch on Numbers 10:5-6

Num 10:5-6

To give the signal for breaking up the camp, they were to blow תּרוּעה, i.e., a noise or alarm. At the first blast the tribes on the east, i.e., those who were encamped in the front of the tabernacle, were to break up; at the second, those who were encamped on the south; and so on in the order prescribed in ch. 2, though this is not expressly mentioned here. The alarm was to be blown למסּעיהם, with regard to their breaking up or marching.