Protip, this is referred to a fireteam(or other unit size) flank in the military world. It can be very effective if done correctly. On a large field this is much easier than said. Having to judge how far out to flank is a crucial component. If you flank to wide the lines may have changed and you may find yourself sitting in the middle of a central firefight, to close and you may get spotted...
If you want to pull this off effectively you need to practice this allot!
sticks