Which preposition to use with culverins

at Occurrences 1%

Many turrets of dark rose color were crowded together upon this narrow, egg-shaped island, where, in other days, the pusillanimous Spanish garrison was locked in the fortress for the purpose of aiming bombards and culverins at the Neapolitans when they no longer wished to pay taxes and imposts.

Which preposition to use with  culverins