An arbalest.

The arbalest was a late variation of the medieval European crossbow . A larger weapon, the arbalest had a steel prod ("bow"). Since an arbalest was much larger than earlier crossbows , and because of the greater tensile strength of steel, it had a greater force. The strongest windlass-pulled arbalests could have up to 5000 lb strength (2267.5 kg) and be accurate up to 500 m. A skilled arbalestier could shoot two bolts per minute. Arbalests were sometimes considered inhumane or unfair weapons, since an inexperienced crossbowman could use one to kill a knight who had a lifetime of training.

This led to their ban by Pope Innocent II, in whose name Canon 29 of the Second Lateran Council (1139, as translated in Decrees of the Ecumenical Councils, ed. Norman P. Tanner) states "We prohibit under anathema that murderous art of crossbowmen and archers, which is hateful to God, to be employed against Christians and Catholics from now on." Note that the anathema was only on the use of these weapons against "Christians and Catholics." In context, this proscription was probably a very late part of a wider, millennial attempt by the Catholic Church to limit warfare, known as the Peace of God movement.

The term arbalest is sometimes used interchangeably with crossbow. 'Arbalest' is French corruption from Roman name arcuballista for crossbow. Notice that modern French uses the word arbalète, not arbalest and do so for both crossbow and arbalest (the latter may be referred to as heavy crossbow but an actual heavy crossbow may not be the same as an arbalest).