As far as I know US mortar crews in all calibers(except one-man mortar) are common to dugged up a pit when it comes into defensive operation.
According to my grandfather, who was an infantry officer in the '50s and '60s, 60 percent of ground warfare consists of digging holes, 20% is moving to a new location for holes, 15% is waiting around in holes, 4% is filling out forms about holes, and 1% is fighting the enemy, usually from holes.