For all armies in Triumph! games there has to be a camp present on the battlefield. The camp serves for no purpose other than being a possible objective for your opponent. You have to protect your camp to prevent it from being sacked. Taking your opponent's camp gives you half the points needed for winning the game.
In my Triumph! games camps are seldom sacked, and when it happens, it is usually done by light cavalry swiftly moving around the enemie's flank and taking the camp before the owner can react to this action. To better protect your camp you may choose one of your fighting units as a garrison, but then it has to remain there and will not participate in the field battle (choices, choices ..).
Now the year is 235 AD and an arabo-aramean army from the city of Hatra is fighting arab nomads on a flat piece of land at the seashore. The Hatra player has deliberately placed his camp at the extreme left of his battleline (using a Battle Card), thus gaining space in the centre for the development of his formation:
arabo-aramaean Hatra at the top,
arab nomads at the bottom of the picture