Even where besiegers outnumbered the besieged by a huge margin it still often took months or even years to defeat a castle by siege, yet if the same two forces

Even where besiegers outnumbered the besieged by a huge margin it still often took months or even years to defeat a castle by siege, yet if the same two forces met in open battle it would be over in an hour or less. This clearly shows that in castle warfare the defence has a huge advantage.