Dora Bas Rivka Silver O'H
Horatio Hornblower (Look it up)
When the Mishkan was completed, G-d's Presence manifested on it in a cloud that appeared as fire overnight. When it was time to travel, the cloud would rise; everybody would pack up and follow it. Sometimes they would camp somewhere for an extended period of time, other times they would just stay for a few days or one night. No matter how long (or short) they camped, they always followed G-d's cue when it came to their travels.
G-d had Moshe make two silver trumpets to assemble the camp and to notify them as to when it was time to move. A long note on both horns was the call for everyone to gather at the Mishkan. On one horn, it was a call just for the leaders to gather. A series of short blasts was the signal to move out, first the eastern division, followed by the southern.
The kohanim were entrusted with these trumpets. When under attack in their homeland, a series of staccato notes would summon the people to battle. These horns would also be sounded on holidays and New Moons, accompanying the sacrifices of the day.