Warfare in Medieval Scotland includes all military activity in the modern borders of Scotland, or by forces originating in the region, between the departure of the Romans in the fifth century and the adoption of the innovations of the Renaissance in the early sixteenth century. In this period conflict developed from minor raids to major conflicts, incorporating many of the innovations of continental warfare.
In the Early Middle Ages war on land was characterised by the use of small war-bands of household troops often engaging in raids and low level warfare. The arrival of the Vikings brought a new scale of naval warfare, with rapid movement based around the Viking longship. The birlinn, which developed from the longship, became a major factor in warfare in the Highlands and Islands. By the High Middle Ages, the kings of Scotland could command forces of tens of thousands of men for short periods as part of the "common army", mainly of poorly armoured spearmen and bowmen. After the "Davidian Revolution" of the twelfth century, which introduced elements of feudalism to Scotland, these forces were augmented by small numbers of mounted and heavily armoured knights. Feudalism also introduced castles into the country, originally simple wooden motte-and-bailey constructions, but these were replaced in the thirteenth century with more formidable stone "enceinte" castles, with high encircling walls. In the thirteenth century the threat of Scandinavian naval power subsided and the kings of Scotland were able to use naval forces to help subdue the Highlands and Islands.