1 9 3 7 , ▁studied ▁one ▁year ▁at ▁commerce ▁school ▁and ▁then ▁moved ▁to ▁Os lo ▁to ▁study ▁drawing ▁and ▁advert ising . ▁ ▁World ▁War ▁II ▁When ▁World ▁War ▁II ▁reached ▁Norway ▁on ▁ 9 ▁April ▁ 1 9 4 0 , ▁with ▁the ▁German ▁invasion , ▁he ▁volunte ered ▁and ▁fought ▁for ▁Norway ▁in ▁the ▁en su ing ▁batt les . ▁He ▁joined ▁Norwegian ▁forces ▁for ▁the ▁first ▁time ▁at ▁V oss ▁and ▁fought ▁in ▁Hall ing dal . ▁After ▁the ▁capit ulation ▁of ▁the ▁regular ▁Norwegian ▁forces , ▁he ▁joined ▁the ▁secret ▁resistance ▁movement ▁as ▁a ▁member ▁of ▁Mil org . ▁Later ▁he ▁became ▁the ▁leader ▁of ▁Mil org ., ▁Ber gen ▁District , ▁from ▁ 1 5 ▁May ▁ 1 9 4 3 ▁until ▁ 2 6 ▁February ▁ 1 9 4 4 ▁when ▁he ▁left ▁the ▁country . ▁ ▁In ▁ 1 9 4 1 ▁S æ len ▁fam ously ▁wrote ▁and ▁illustrated ▁the ▁book ▁S nor re ▁Sel ▁(" S nor ri ▁the ▁Se al "). ▁The ▁book , ▁subt itled ▁" A ▁f able ▁in ▁colors ▁for ▁adult s ▁and ▁children ", ▁was ▁a ▁subt le ▁sat ire ▁on ▁Naz i ▁Germany , ▁and ▁was ▁widely ▁read ▁and ▁later ▁translated ▁to ▁several ▁languages . ▁It ▁was ▁soon ▁b anned ▁by ▁the ▁Nas j onal ▁Sam ling ▁us ur p ant ▁authorities . ▁In ▁ 1 9 4 2 ▁he ▁followed ▁with ▁Tre ▁kal de ▁kar er ▁(" Three ▁Cold ▁F ell ows "), ▁car ic