Until at least the 11th Century, several military manuals of the Byzantine Empire proscribe using slings to supplement close-range firepower for the army's advance, and for use during sieges. For centuries, all Byzantine soldiers were required to carry slings as backup weapons in case their primary ranged weapons were damaged in battle. The use of small stone projectiles in general is also commonly described. Leo VI's Taktika suggests that when all else fails, that naval soldiers should keep on hand a supply of rocks to hurl at the enemy when their other weapons had run out. However, despite these descriptions, the use of slings in Byzantine armies does seem to have declined significantly by the turn of the millennium (AD 1000) and even moreso after the fall of Constantinople in AD 1204.

The decline of the sling's use amongst Europeans is likely due to the fact that it only had a limited effective range (perhaps 75 yards at most to lay an accurate killing blow against an armored opponent, despite having a flight range of possibly up to 300+ yards), required a huge amount of training to throw accurately and a good deal of space to use in battle formation (preventing use in tight-knit units), and with increasing prevalence of heavy armor (i.e. mail and plate) amongst European forces in the latter years of the Middle Ages, the effectiveness of the sling became more and more lackluster. By the 1300s, weapons such as the crossbow allowed for even a peasant with minimal training the capability to take down a powerful, heavily-armored, and superbly-trained knight at the flip of a lever. While the sling could knock a knight off of his horse, the fact that the weapon could only do so at close range meant that slingers (who were often poorly equipped anyways) would have been easily hacked to pieces if a melee ensued, not to mention would have been at risk anyways from a cavalry charge. Along this line of thought, slings were also awkward to use whilst mounted on horseback (and remained vastly less effective cavalry weapons than composite bows or javelins), and this would have further destroyed its usefulness on the battlefields of later medieval Europe. And finally, since they required a lot of space to operate, using them to fire from the increasingly narrow arrow slits of medieval castles became virtually impossible.

All of these factors likely led to the decline of the sling's use as a primary weapon of war, although as a cheap defense or hunting weapon, it still probably maintained popularity in some locales into 1500s and beyond.