The speed necessary for a successful impact depended on the angle of attack; the greater the angle, the lesser the speed required. At 60 degrees, 4 knots was enough to penetrate the hull, but this increased to 8 knots at 30 degrees. If the target for some reason was in motion towards the attacker, less speed was required, especially if the hit came amidships. War galleys gradually began to develop heavier hulls with reinforcing beams at the waterline, where a ram would most likely hit. There are records of a counter-tactic to this used by Rhodian ship commanders where they would angle down their bows to hit the enemy below the reinforced waterline belt. Besides ramming, breaking enemy oars was also a way to impede mobility and make it easier to drive home a successful ramming attack.