The standard map symbol for a field army. The four exes are the generic symbol of a field army (i.e. they do not represent Roman numerals); the army's specific number or name, if included, would be written numerically to the left of the symbol.
A field army is a military formation. It is made up of two or more corps. Two or more field armies can form an army group. A field army is usually commanded by a general or a lieutenant general.