The Mortar is a long ranged Weapon Team manned by a crew of three. Loader, gunner and spotter. Although only two are needed to man it. American and Wehrmecht forces both have access to Mortar Infantry, while British forces can take it as a fixed emplacement or Commando Mortar teams if the Commander chooses the Commando tech tree, and Panzer Elite have access to a highly mobile mortar mounted on a Halftrack.
Mortar teams work most efficiently used as backup for advancing assaults, especially infantry. Their long range allow them to bombard an area from safety prior to an attack, thus weakening enemy defenses. The mortar rounds are most efficient against pinned infantry, structures, and finishing off immobilized or slow moving vehicles. Wehrmacht and American mortars can carry smoke rounds that work as a screen providing cover for advancing infantry. Mortars are also dropped when the manning squad is killed so they can be looted by infantry and used against their original owner, or resecured at no cost.
The only armament other than the mortar in a squad is a pistol or light SMG used by the spotter. The weapon also needs to be packed and unpacked when it comes to redeploying. It is then very easy for a Mortar team to be killed if caught unawares. It is therefore best if deployed not far behind your lines in a secure area where they can aid advancing assaults or defenses.