Having decided to surrender, ENOMOTO sent his 'Bankoku Kairitsu Zensho (a compendium of international marine laws)' by Ortolan (which was a copy made by ENOMOTO himself on which he added many footnotes and other comments), which he had carried with him continually since he was in the Netherlands, to Ryosuke KURODA (Kiyotaka KURODA), a general staff of the punitive forces against Ezo, hoping it would not be lost in the battle.
降伏を決意した榎本は、オランダ留学時代から肌身離さず携えていたオルトラン著「万国海律全書」（自らが書写し数多くの脚注等を挿入）を戦災から回避しようと蝦夷征討軍海陸軍総参謀黒田了介（黒田清隆）に送った。