Hello,
Shields work at the first stage of combat. For example, if you have 10 drillers and 10 shield, and an enemy attacks with 15 drillers, first the 10 shield will be drained, and then 10 drillers will kill 5 of them, with 5 drillers and 0 shields remaining.
Imagine how stupid the average person is. Then realize that half of the people are even stupider than that.
-George Carlin