Thatdayissearedintothememoryofeveryhumanbeingontheplanet:thedaytheworldchanged.FirstcametheattackonthePhilippines.Withindaystheyspread,asthoughappearingoutofnowhere,strikingoutatmoreislands,forgingafootholdintheSouthPacific.ThencamethefirstattackonU.S.soil-LosAngeles-andtherealitybecameclear:ourworldwasatwaronceagain,butthistimewithanenemyfrombeyondourgalaxy.Now,monthslater,thefateoftheworldhangsinthebalanceasamissiontostrikeatakeyenemyinstallationdeepinenemyterritorygoesterriblywrong,andtheMarinesofthe15thExpeditionaryUnitarescatteredacrosstheislandofNewBritain,leaderless,andfacingimpossibleodds.PacificTheateristhestoryofthoseMarines:freshrecruitswhojourneyfromtheirhomesacrossthePacifictothefrontlines.ItisthestoryofJohnBlake,acharmingCaliforniansurferwhomustfindthestrengthtobeealeader,TraceyGleeson,aphysics..
