Warships of the age of sail were highly vulnerable to fire. Made of wood, with seams caulked with tar, ropes greased with fat, and stores of gunpowder, there was little that would not burn. Accidental fires destroyed many ships, so fire ships presented a terrifying threat. With the wind in exactly the right direction a fire ship could be cast loose and allowed to drift onto its target, but in most battles fire ships were equipped with skeleton crews to steer the ship to the target (the crew were expected to abandon ship at the last moment and escape in the ship's boat). Fire ships were most devastating against fleets which were at anchor or otherwise restricted in movement. At sea, a well-handled ship could evade a fire ship and disable it with cannon fire. Other tactics were to fire at the ship's boats and other vessels in the vicinity, so that the crew could not escape and therefore might decide not to ignite the ship, or to wait until the fire ship had been abandoned and then tow it aside with small maneuverable vessels such as galleys.