There are two different ranged attack options. One is
Ranged Bombardment and the other is
Archer Bombard. Both can be turned on or off in the BUG menu (Ctrl-Alt-O) under the
RevDCM tab.
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Ranged Bombardment allows a Siege unit that can deal collateral damage (Ballista and up, not Rams) to deal collateral damage to a stack without damaging itself or damaging the lead unit. It uses the same icon as Bombard. I am almost certain that trying to use Ranged Bombardment on a city whose defenses have not yet been reduced to 0% will act as Bombard first and reduce the defenses, although it seems to act strangely with units selected in a stack.
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Archer Bombard can be used to attack enemy units without risking the unit, but there is a good chance it can miss and it requires several bombardments to kill a unit. Archer Bombard is allowed by an XML flag. There is no promotion that can grant it. Archer units, Siege units, Grenadier and Modern Grenadier, some late-game Mecha units, and a lot of later naval units have this capacity. Most Gunpowder units do NOT have this ability. This is deliberate.
If you have an eligible unit, the blue Archer Bombard icon will appear. Click that and you should get a yellow rounded square around a unit that can be bombarded. Then click to attempt bombardment.
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If it hits, it will say
Your X has attacked an enemy Y (Z% damage) . The display is slightly bugged; it actually displays the damage taken BEFORE the bombardment. However, the unit really is damaged. After bombarding with an Archer that listed 0% damage, the Lion actually took 45%.
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I would first check your BUG options to see if your buttons are checked. If that doesn't work, we will have to dig deeper.