lewis gun - more portable firepower able to put alot more lead down range. could move this one around alot more efficently than others like the maxim
maxim water cooled though was less portable but was more reliable. it was a mounted machine gun.
reasons as to why trench warefare originated.. more deadly machines, less mobility because of more lead coming your way. would lead to tanks and other protective vehicles being developed to try and break the stale mate.