Siege units and some naval units can bombard land and naval units (for a chance to cause damage to one unit's hit points), tiles (to destroy improvements) and cities. The bombard ability usually cannot be used to kill units, the Hwacha being an exception.
When bombarding a unit, the bombarding unit's Bombard value is compared with the other unit's Defense value (a function of its Defense pips and Defender Combat Bonus). Thus, a Catapult (with a Bombard of 4) bombarding a Musketman (with a Defense of 4) would, neglecting defender combat bonus, have a 50% chance of inflicting one hit point of damage.
Rate of fire Edit
The process above takes place against the same defending unit a number of times equal to the bombarding unit's rate of fire. Thus, the bombarding unit can inflict no more damage when ordered to bombard than its rate of fire.
Defensive bombard Edit
A siege unit will, upon its tile being attacked, fire once at the attacking unit for a chance to lower its hit points before fighting between land units ensues, providing that the siege unit has not already performed a defensive bombard that turn, and that no siege unit on the same tile has already performed a defensive bombard during that particular attack. This will occur regardless of whether the siege unit fired during its own civilization's turn.
Bombardment in Ports Edit
Naval units "in port" (i.e., in a coastal city square being bombarded) are especially vulnerable to bombardment attacks, simulating that a ship moored at a dock, or at anchor, is unable to quickly maneuver.