Armed with their innovative exploding shells, the stalwart Mortar Teams of Ironforge are capable of blasting apart enemy ranks from long range. These fearless dwarves are masters of explosive devices and relish in pounding fortified enemy emplacements to dust.
Mortar Teams have the largest area of effect damage of all the siege units. Mortar Teams are good at killing buildings. Bring them along when you are assaulting an enemy town. Mortar Teams cannot attack air units.
If you use a lot of Mortar Teams be sure to at least research the damage upgrades to make them more effective.
Mortar Teams will damage your own units so be careful to prevent them from killing your own army.
Mortar Teams can be used to clear away trees.
Mortar Teams are the only ranged siege units in the game that aren't mechanical, so you can cast invisiblility on them, run them into the back of an enemy base with a couple sorceresses, and when the enemy comes back to kill the Mortar teams, cast invisiblility and run away! Also you can cast spells like Inner Fire on them too, which can help a lot in team games. Beware though, this can be used against you, with spells like Storm Bolt and Polymorph which affect non-mechanical units too.