Once I get howitzers all hell breaks loose. Half a dozen howitzer units or more kills everything. In buildings, behind walls, in woods, behind hills, in fortresses: nowhere is safe from massed exploding / carcass / quick lime / percussion shells. Infantry kills everything that tries to get at the front / flanks of my artillery. Cavalry kills everything that tries to attack the rear / flanks of my artillery. Sometimes I finish up occupied buildings with bayoneting line infantry rather than artillery because they get easy chevrons that way.