Combined arms military actions are operations that involve the coordinated actions of different branches of types of ground troops (e.g., infantry, tanks, artillery), or multiple branches of service (e.g., Army, Marines, Navy, Air Force). Traditionally, a staff that dealt with multiple types of ground troops had "G" prefixes for its sections, while a staff that dealt with multiservice operations had "J" for "joint" branches.
In the Second World War, the British term was "combined operations". German blitzkrieg worked at two levels: the high-speed breakthrough by coordinated tanks, motorized infantry, artillery, and close air support; followed by securing the flanks by conventional infantry.
While the term has been used to describe multinational operations, those are more commonly called "coalition" operations; a staff integrating multiple countries has "C" sections.