As a static structure, castles could often be avoided. Their immediate area of influence was about and their weapons had a short range even early in the age of artillery. However, leaving an enemy behind would allow them to interfere with communications and make raids. Garrisons were expensive and as a result often small unless the castle was important. Cost also meant that in peacetime garrisons were smaller, and small castles were manned by perhaps a couple of watchmen and gate-guards. Even in war, garrisons were not necessarily large as too many people in a defending force would strain supplies and impair the castle's ability to withstand a long siege. In 1403, a force of 37 archers successfully defended Caernarfon Castle against two assaults by Owain Glyndŵr's allies during a long siege, demonstrating that a small force could be effective.