At the second blast the camps on the south set out. The long blasts are the signals to march.
The bugle call that gathers the assembly is different from the signal to march.
"The sons of Aaron, the priests, are in charge of blowing the bugles; it's their assigned duty down through the generations.
When you go to war against an aggressor, blow a long blast on the bugle so that God will notice you and deliver you from your enemies.
Also at times of celebration, at the appointed feasts and New Moon festivals, blow the bugles over your Whole-Burnt-Offerings and Peace-Offerings: they will keep your attention on God. I am God, your God." The March from Sinai to Paran
In the second year, on the twentieth day of the second month, the Cloud went up from over The Dwelling of The Testimony.
At that the People of Israel set out on their travels from the Wilderness of Sinai until the Cloud finally settled in the Wilderness of Paran.
They began their march at the command of God through Moses.
The flag of the camp of Judah led the way, rank after rank under the command of Nahshon son of Amminadab.
Nethanel son of Zuar commanded the forces of the tribe of Issachar,
and Eliab son of Helon commanded the forces of the tribe of Zebulun.