A troop of soldiers: in formation bravely they stand
An ominous rumble is heard across the land
Then, boom! A blast, they are struck down - fallen, slain
But rise from the grave to face danger again
A troop of soldiers: in formation bravely they stand
An ominous rumble is heard across the land
Then, boom! A blast, they are struck down - fallen, slain
But rise from the grave to face danger again
Explain what this is describing.
Edit: made a small change to make the solution less obvious.