根据韩战期间真实战事改编。1950年6月25日，北韩挥军越过三八线突袭南韩，三日攻陷汉城（今首尔），战线不断南进。在美军及联合国军支援下，南韩军逆势反击。美军指挥官麦克亚瑟提出代号为「铁铬行动」的仁川登陆计划，该计划急需一支大队的兵力从侧翼阻击扰敌、声东击西，通过长沙里切断北韩军的补给线。
由于任务本身极其艰钜，加上南韩国军当时兵力薄弱，无法抽调足够正规军支援，军方不得不把这项任务交付给772名学生兵执行，这些学生兵平均年龄只有17岁，仅仅接受了两星期的军事训练，在毫无实战经验的情况下投身战场。行军路上固然杀机重重，战友内部也诸多衝突，年少气盛，迸发出各种角力。
仁川登陆战前夕，长沙里登陆任务如期执行，这群徒有一腔热血但战力薄弱的学生们，无可避免地接受命运中最残酷的考验：穿越炮火与海浪，浴血长滩，馀下部队身陷敌军重重围剿，直至弹尽粮绝，挣扎于阵亡与倖存的分界线上…
BasedontheincredibletruestoryofJangsariLandingOperation.WhenNorthKoreainvadesSouthKoreaonJune25,1950,theypushedSouthKoreaanditsallyUSArmytothesouthernmostcity.U.S.GeneralMacArthurplannedOperationChromite,whichwouldseethejointalliedforcestotakebackastrategiclocationofInchonandinorderforittosucceed,heneededasmallbattaliontoflanktheNorthKoreanarmyandeliminatetheirsupplylineatJangsaribeach.
HavinglosthisfamilyonhisretreatawayfromNorthKoreabeforetheWar,amodelstudentChoiSung-pilenlistsinthearmytofightfortheSouth.KiHa-ryunisarebelliousyouthfromtheSouthwhovolunteerstofightinthewar.Allofthe772studentsandyouthsarelikethemwhoarebarelyoutofschoolwithonly2weeksofbootcamptraining.TaskforcemanderCaptainLeeMyung-junknowsthatit’salongshot,buthehasnochoicebuttoleadthemintoacrucialmission.Meanwhile,USwarcorrespondentMaggiebravesthedangersofthebattlefieldtoreportonthewarinthefrontlines.ShefeelsempathyfortheKoreanstudentswhomustgointobattleonbehalfoftheveteransoldiersfortheircountry,andtriestodowhatshecanonherendtorescuethem.
Withlittleammo,scantfoodsuppliesandraggedyweapons,canthestudentssuccessfullycarryouttheirmissionandreturnhomesafely?
