It means that everybody was involved in the grenade battle. To bring everyone to their feet means that they were first sitting down, relaxing, off duty in that moment from fighting, but once the grenade battle began, it was so intense that it required the use of all soldiers, therefore bringing everyone to their feet. In another context you could say that ' the performance of the actors was so impressive that it brought the entire audience to their feet' meaning that the audience literally stood up (from being seated) and began applauding. In both contexts it basically means that the people go from being not involved, to involved (to their feet) and are an active part of what is happening (either returning fire in the battle, or clapping their hands because they were impressed by the performance) Hope this helps!

Hello! That phrase means that the grenade battles alarmed and made the garrison alert and ready to fight.

The phrase has three meanings. The first is the straightforward one of "make someone need to stand-up". The garrison couldn't just keep on sleeping, they had to get out of bed and respond to the battle. The second is also fairly physical and means to stand up because you are enjoying an artistic performance so much. "the encore brought the entire audience to its feet". They are probably clapping and cheering. The final one is the metaphorical version of these. A letter from the company chairman might bring the sales to department to their feet because they had been slacking and need to respond, or because it was so inspiring they felt like cheering. After all of that, I would guess that this passage is using the first of these meanings. The garrison had to get out of bed and return to active duty.