The earliest crossbow-like weapons in Europe probably emerged around the late 5th century BC when the "gastraphetes", an ancient Greek crossbow, appeared. The device was described by the Greek author Heron of Alexandria in his "Belopoeica" ("On Catapult-making"), which draws on an earlier account of his compatriot engineer Ctesibius (fl. 285–222 BC). According to Heron, the gastraphetes was the forerunner of the later catapult, which places its invention some unknown time prior to 399 BC. The gastraphetes was a crossbow mounted on a stock divided into a lower and upper section. The lower was a case fixed to the bow while the upper was a slider which had the same dimensions as the case. Meaning "belly-bow", it was called as such because the concave withdrawal rest at one end of the stock was placed against the stomach of the operator, which he could press to withdraw the slider before attaching a string to the trigger and loading the bolt; this could thus store more energy than regular Greek bows. It was used in the Siege of Motya in 397 BC. This was a key Carthaginian stronghold in Sicily, as described in the 1st century AD by Heron of Alexandria in his book "Belopoeica".