John II Casimir Vasa
In late 1648 the newly elected king John II Casimir Vasa, who had no plans for the war with Ottomans, advised him to return to the Netherlands and publish his studies there. There are rumors that in 1649 Siemienowicz became embroiled in a conflict with General of the Artillery Krzysztof Arciszewski over a bureaucratic matter; around 1649 he decided to leave the Commonwealth and work on his book in Amsterdam.