▁water ▁( e . g ., ▁the ▁N ara ▁and ▁N er is ▁rivers ). ▁Arch ae olog ists ▁have ▁exc av ated ▁many ▁bur ial ▁m ounds ▁of ▁the ▁Balt ic ▁and ▁S lav ic ▁people ▁that ▁lived ▁around ▁Nar ach . ▁ ▁Since ▁the ▁Middle ▁A ges , ▁the ▁local ▁inhabitants ▁have ▁lived ▁mainly ▁by ▁fish ing ▁and ▁far ming . ▁In ▁the ▁ 1 9 th ▁century , ▁the ▁most ▁prof itable ▁work ▁was ▁fish ing ▁of ▁c ray fish . ▁In ▁the ▁ 2 0 th ▁century , ▁the ▁e el ▁became ▁the ▁main ▁market able ▁fish . ▁ ▁During ▁World ▁War ▁I , ▁the ▁surrounding ▁area ▁was ▁a ▁foc al ▁point ▁of ▁the ▁Lake ▁Nar och ▁Off ensive ▁( M arch – A pril ▁ 1 9 1 6 ), ▁an ▁incon clus ive ▁off ensive ▁operation ▁mounted ▁by ▁forces ▁of ▁the ▁Imperial ▁Russian ▁Army ▁against ▁the ▁German ▁army . ▁ ▁In ▁ 1 9 1 9 , ▁German ▁composer ▁Sieg fried ▁Wagner ▁set ▁to ▁music ▁a ▁poem ▁by ▁Gün ther ▁Hol stein ▁( 1 8 9 2 - 1 9 3 1 ) ▁about ▁a ▁military ▁battle , ▁called ▁Nach t ▁am ▁Nar ocz ▁( N ight ▁at ▁lake ▁Nar ach ). ▁ ▁In ▁the ▁ 1 9 3 0 s , ▁the ▁fish ers ▁of ▁Nar ach ▁rose ▁against ▁Polish ▁authorities ▁def ending ▁their ▁right ▁to ▁explo it ▁the ▁lake . ▁ ▁Since ▁the ▁ 1 9 5 0 s , ▁the ▁lake ▁has ▁become ▁a