Under the republic Roman consul was responsible for leading armies into battle. Usually each of the two annual consul was responsible for a force of 2 legions, called a consular army. That force can be expanded to 4 legions if the circumstances warrants.
But in times of National emergency the two consular armies can be combined into a single force. When this occurs each consul is responsible for the entire army on alternate days. This leads to interesting command and control issues when the two consuls do not see eye to eye regarding how to conduct a campaign. According to Livy, this arrangement was responsible for the single most calamitous battlefield defeat the Roman’s ever suffered, when 8 Roman legions were almost completely annihilated by a force half as big and commanded by Hannibal at the battle of Cannae.
But in times of National emergency the two consular armies can be combined into a single force. When this occurs each consul is responsible for the entire army on alternate days. This leads to interesting command and control issues when the two consuls do not see eye to eye regarding how to conduct a campaign. According to Livy, this arrangement was responsible for the single most calamitous battlefield defeat the Roman’s ever suffered, when 8 Roman legions were almost completely annihilated by a force half as big and commanded by Hannibal at the battle of Cannae.
