' s ▁Collect ed ▁Works . ▁ ▁From ▁Yan ' an ▁Ber tr am ▁set ▁out ▁for ▁the ▁E ighth ▁Route ▁Army ▁headquarters ▁in ▁southern ▁Sh an xi ( Sh ans i ) ▁and ▁travel led ▁for ▁five ▁months ▁with ▁the ▁army ▁in ▁northern ▁China . ▁ ▁On ▁the ▁day ▁that ▁he ▁crossed ▁the ▁Y ellow ▁River ▁from ▁Sh a an xi ( Sh ens i ) ▁back ▁to ▁Sh an xi , ▁this ▁time ▁by ▁boat , ▁Tai y uan ▁the ▁Sh an xi ▁capital ▁fell ▁to ▁the ▁Japanese . ▁Most ▁of ▁his ▁time ▁was ▁spent ▁with ▁the ▁troops ▁of ▁General ▁He ▁Long ( H o ▁L ung ). ▁Based ▁on ▁these ▁experiences ▁behind ▁the ▁front ▁Ber tr am ▁wrote ▁a ▁book ▁North ▁China ▁Front ▁( 1 9 3 9 ). ▁ ▁Rel ief ▁work ▁and ▁M me ▁Sun ▁Y at - sen ▁Ber tr am ▁began ▁to ▁more ▁act ively ▁support ▁China ' s ▁war ▁against ▁the ▁Japanese , ▁and ▁carried ▁out ▁aid ▁work ▁with ▁the ▁China ▁Def ence ▁League ▁( CD L ) ▁under ▁Madame ▁Sun ▁Y at - sen ▁( So ong ▁Ch ing - ling ). ▁ ▁The ▁CD L ▁was ▁a ▁relief ▁committee ▁formed ▁in ▁Hong ▁Kong ▁to ▁help ▁maintain ▁Norman ▁Beth une ▁and ▁the ▁International ▁Peace ▁H osp it als ▁in ▁China ' s ▁northern ▁war ▁area . ▁During ▁this ▁time ▁Ber tr am ▁gave ▁fund - ra ising ▁lect ures ▁in ▁the ▁US ▁and ▁led ▁a ▁con voy ▁of ▁supply ▁tr uck s ▁with ▁pet