▁easily ▁into ▁ 7 4 - man ▁bar ra cks . ▁By ▁slightly ▁increasing ▁the ▁bar ra cks ▁size , ▁substantial ▁sav ings ▁were ▁made ▁by ▁reducing ▁the ▁overall ▁number ▁of ▁buildings ▁that ▁needed ▁to ▁be ▁constructed , ▁the ▁size ▁of ▁the ▁canton ment ▁areas ▁required , ▁and ▁the ▁length ▁of ▁required ▁roads ▁and ▁utility ▁lines . ▁Case y ▁was ▁promoted ▁to ▁lieutenant ▁colon el ▁on ▁ 8 ▁April ▁ 1 9 4 1 . ▁ ▁On ▁the ▁afternoon ▁of ▁Th urs day , ▁ 1 7 ▁July ▁ 1 9 4 1 , ▁Som erv ell ▁sum mon ed ▁Case y ▁and ▁Berg st rom ▁and ▁gave ▁them ▁a ▁new ▁special ▁project : ▁the ▁design ▁of ▁an ▁enorm ous ▁office ▁complex ▁to ▁house ▁the ▁War ▁Department ' s ▁ 4 0 , 0 0 0 - person ▁staff ▁together ▁in ▁one ▁building . ▁Som erv ell ▁gave ▁them ▁until ▁ 0 9 : 0 0 ▁on ▁Monday ▁morning ▁to ▁design ▁the ▁building , ▁which ▁he ▁en vis aged ▁as ▁a ▁modern , ▁four - story ▁structure ▁with ▁no ▁elev ators , ▁on ▁the ▁site ▁of ▁the ▁old ▁Washington ▁Ho over ▁Airport . ▁ ▁This ▁would ▁ultimately ▁become ▁The ▁Pent agon , ▁the ▁largest ▁office ▁building ▁in ▁the ▁world . ▁ ▁Over ▁that ▁" very ▁busy ▁week end ", ▁Case y , ▁Berg st rom ▁and ▁their ▁staff ▁rough ed ▁out ▁the ▁design ▁for ▁a ▁four - story , ▁five - s ided ▁structure ▁with ▁a ▁floor ▁area ▁of ▁— tw ice ▁that