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Answer: Anindya has successfully cracked this! It is Thin Red Line. Awesome answer!!
The battle scene shown in the painting was part of the Battle of Balaclava in Crimean War. You can see the infantry-men wearing red tunics and standing in a two deep formation to take on the cavalry of the Imperial Russian forces. The general practice in those days were to have the infantry stand in at least a four deep formation, in case they were deployed in a line. That's why it was called the Thin Red Line.
The Hollywood movie of the same name is based on a later incidence, which happened during the Pacific campaign of WWII.