A military column is a formation of soldiers marching together in one or more files in which the file is significantly longer than the width of ranks in the formation. The column formation allowed the unit rapid movement, a very effective charge (due to weight of numbers) or it could quickly form square to resist cavalry attacks, but by its nature only a fraction of its muskets would be able to open fire.
The previously prevalent formation, the line, offered a substantially larger musket frontage allowing for greater shooting capability but required extensive training to allow the unit to move over ground as one while retaining the line.
It is also applied by modern armies to vehicles, troops and naval vessels.
During the early stages of the French Revolutionary Wars, battalions in French armies often attacked in column formation in an attempt to drive through enemy lines by sheer weight of numbers. Against enemy units already weakened by the fire from skirmishers or artillery, this was often successful. Later, during the Napoleonic Wars, French units would approach in column formation and deploy into line when close to the enemy. However, against the British they frequently failed to deploy into line before being engaged. During the Peninsular War, after the Battle of Sabugal (3 April 1811), the Duke of Wellington wrote, "our loss is much less than one would have supposed possible, scarcely 200 men... really these attacks against our lines with columns of men are contemptible."  These failings were still evident at the Battle of Waterloo in 1815, prompting Wellington to comment, "They came on in the same old way and we defeated them in the same old way."
The military historian James R. Arnold argues that all armies of the period used column formations at times on the battlefield; the military historian Sir Charles Oman is credited with developing the theory that the French practically always attacked in heavy columns, and it is only now that this alleged error, propagated by other British and American authors, is being repudiated.
During the Peninsular War, British riflemen of Craufurd's Light Division marching to engage the enemy but uncertain of the presence of enemy cavalrymen in the area could adopt a formation called "column of companies." Each company would form into two ranks of about thirty files and march close to the company in front. If attacked by cavalry, they could easily bunch up, forming a schiltron of bayonets that would be proof against unsupported cavalry.
The column formation was extensively used by Chinese infantry during the Korean War. When attacking, the Chinese would form their assault units into deep columns of platoons or squads, and drove such formations into the weak points of the enemy's defenses. The rationale for such a tactic was that repeated assaults conducted by squad- or platoon-sized skirmish parties would eventually penetrate enemy lines through sheer attrition. This utilization of column formation also give birth to the term human wave attack.