the Roman vessel around a pole. This construction allowed the bridge to be swung port to starboard and therefore used on either side of the ship. A pulley at the top of the pole allowed the planks to be raised and lowered on command. At the end of the bridge there was a heavy metal spike that when dropped on the deck of an enemy ship would, with the aid of gravity, become imbedded in the deck. By connecting the two ships in such a way, Roman soldiers could gain access to the deck of the enemy ship and engage in hand-to-hand combat instead of depending on ship-to-ship combat. Polybius also includes an insight on how these siege engines would have practically functioned in battle: And as soon as the "crows" were fixed in the planks of the decks and grappled the ships together, if the ships were alongside of each other, the men leaped on board anywhere along the side, but if they were prow to prow, they used the "crow" itself for boarding, and advanced over it two abreast. The first two protected their front by holding up before them their shields, while those who came after them secured their sides by placing the rims of their shields upon the top of the railing. Such were the preparations which they made; and having completed them they watched an opportunity of engaging at sea.Based on this historical description the Corvus used some mechanisms seen in the more complex siege towers or the sheds constructed around battering rams. They protected, to an extent, the Roman soldiers as they gained entry to the enemy's space where they could engage in combat. See also Notes References