"Fire!" Re'Rak shouted. A soldier stationed at the bottom of the tower blew into a trumpet. The trumpet had been designed specifically to relay instructions over long distances. It had vents at numerous places, designated based on the trenches dug within the ground within which the soldiers hid.
It was muffled at the area of reception to ensure the sound wouldn't leak out of their hiding spot. Moreover, the words used were different from those used in day-to-day conversations. They had unique, non-repeating pronunciations to ensure the receptor wouldn't misunderstand the message.
The moment the soldier trumpeted the signal to open fire, the soldiers hiding within all the trenches aimed with their crossbows. Crossbows consumed less space, as they didn't need the draw length during the time of firing. So, it made the perfect weapon to use in their current situation where they were huddled close to each other.