He served as Prussian field marshal and was appointed Governor of Berlin, but never filled the latter position.

Duke Fredrick William subsequently renamed the second manor Holstein (now in Pregolskiy, Kaliningrad).

In 1732, he purchased Haus Beck, near Ulenburg, Minden-Ravensberg, after which the Schleswig-Holstein-Sonderburg-Beck line was named, from Duchess Maria Antonia (1692-1762), the widow of his cousin Frederick William I (1682–1719), who had converted to Catholicism and had become a field marshal in the Army of the Holy Roman Empire.

[1] The duke was promoted to field marshal later that year and posted in Königsberg, the capital of East Prussia.

[4] In 1745, Frederick William II re-sold Haus Beck in North Rhine-Westphalia to Magdalena Dorothea, Baroness von Ledebur-Königsbrück, née von Nagel zu Wallenbrück (d. 1750), but retained the title Duke of Schleswig-Holstein-Sonderburg-Beck, although in name only, without an allodial estate.

Frederick William was married twice: 1) His first wife was Louise Felicitas Eleonora of Loß, Countess of Dabrova (d. 1715).

She was the widow of a Prince Antoni Dominik Czartoryski (1673-1695) and a daughter of the Polish treasurer Wladislav of Loß, Duke of Marienborg and his Swedish wife, Baroness Barbara Gyllenstierna.