Answer: war

AnswerCrossword Clue
WARCard game requiring no skill
WARStrategy-free card game
WARTheater goings-on
WAROne of the Four Horsemen
WAROpen hostilities
WARSherman's "hell"
WARKids' card game for two
WAR"Politics with bloodshed": Mao Zedong
WARSun Tzu's area of expertise
WARCabinet department that split in 1947
WARCampaigner's contest (or the start of a 1930s movie actor's split personality)
WARAffair of Ares
WARChild's card game
WARHighest-card-wins game
WAR".. and Peace"
WARKind of game or story
WARSerious conflict
WARStruggle
WARArmed conflict
WARBasic card game
warperiod of such armed conflict
WARPeace, per Big Brother
WAREndless card game
WARHell, to Sherman
WARTrojan, for one
WAROld Maid alternative
WARAll-out fight
WARHostile encounter
WARIt's hell
WARTwo-player card game
WARCommon video game milieu
WARConflict
WARCard game that is (aptly) arbitrary and seemingly neverending
WARKids' card game
WAR1914 headline
WARHostilities
WARGame of sheer luck
WARSeries of skirmishes
WARCombat
WARAres's realm