As well as writing notable verse and hymns, he spent several years accompanying the Duke of Holstein's embassies to Russia and Persia.

[2][3] The Thirty Years' War drove Fleming to Holstein,[3] where in 1633 Frederick III, Duke of Holstein-Gottorp, engaged him as physician, courtier and steward.

Towards the end of 1633 the Duke sent Fleming with Adam Olearius as a member of an embassy to Russia and the Persian Empire headed by Otto Brüggemann and Philipp Kruse.

After four months in the capital city, the Holstein embassy departed again for the Baltic on Christmas Eve, 1634, and on 10 January 1635 arrived at Reval (now Tallinn) in Swedish Estonia.

On returning to Reval, Fleming found that Elsabe had married another man and became engaged to her sister, Anna Niehus.

[2] Fleming's well-known poems include Auf den Tod eines Kindes (On the Death of a Child) and Madrigal.

[6] The only collections published in his lifetime were Rubella seu Suaviorum Liber (1631) and Klagegedichte über das unschuldigste Leiden und Tod unsers Erlösers Jesu Christi (Laments concerning the most innocent Suffering and Death of our Saviour Jesus Christ), printed early in 1632, the second of which begins with an invocation of Melpomene, the Muse of tragedy.

[18] Fleming wrote the hymn in nine stanzas "In allen meinen Taten" (In all that I do) on the melody of "Innsbruck, ich muss dich lassen" by Heinrich Isaac,[19] which is contained in several hymnals.