During the later Roman Empire, the principal military developments were attempts to create an effective cavalry force as well as the continued development of highly specialised types of troops. The creation of heavily armoured cataphract-type soldiers as cavalry was an important feature of the 5th-century Roman military. The various invading tribes had differing emphasis on types of soldiers—ranging from the primarily infantry Anglo-Saxon invaders of Britain to the Vandals and Visigoths, who had a high proportion of cavalry in their armies. During the early invasion period, the stirrup had not been introduced into warfare, which limited the usefulness of cavalry as shock troops because it was not possible to put the full force of the horse and rider behind blows struck by the rider. The greatest change in military affairs during the invasion period was the adoption of the Hunnic composite bow in place of the earlier, and weaker, Scythian composite bow. Another development was the increasing use of longswords and the progressive replacement of scale armour by mail armour and lamellar armour.