John V, Duke of Saxe-Lauenburg

After a fire John V reconstructed Saxe-Lauenburg's residential castle in Lauenburg upon Elbe, started in 1180–1182 by Duke Bernard I.^[2]

In 1481 John V redeemed Saxe-Lauenburg's exclave Land of Hadeln, which had been pawned to Hamburg as security for a credit of 3,000 Rhenish guilders since 1407.^[3] John V then made his son and heir apparent, Magnus, vice-regent of Hadeln, and finally regent as of 1498.^[4]

Having advanced to regent Magnus, who in 1484 had failed to conquer the rich Land of Wursten, a de facto autonomous region of free Frisian peasants in a North Sea marsh at the Weser estuary, won his father and Henry IV the Elder of Brunswick and Lunenburg, Prince of Wolfenbüttel on 24 November 1498 as allies in a second attempt to conquer Wursten.^[5][6] However, on 9 September 1499 the pre-emptive feud of the joint forces of Wursten, the Prince-Archbishopric of Bremen, Ditmarsh, the cities of Bremen, Buxtehude, Hamburg, and Stade against John V and Magnus turned the latter's campaign into an adventure involving heavy losses.^[4] By early December 1499 Prince-Archbishop Johann Rode of Bremen converted Henry IV to their column so that Magnus lacked support.^[7]

Mediated by Eric I of Brunswick and Lunenburg, Prince of Calenberg and Henry IV, Rode and Magnus for his father John V concluded peace on 20 January 1500.^[7] Hadeln was restored to Magnus, while the Wursteners rendered homage to Rode on 18 August, thus in the end little had changed as compared with the status quo ante.^[8]

On 12 February 1464 John V married Dorothea of Brandenburg (1446 – March 1519), daughter of Frederick II, Elector of Brandenburg, and they had the following children:

• Adelheid (*?–died as a child*)
• Sophia (*died latest 1497*), on 29 November 1491 ∞ Antonius of Schaumburg [de]
• Magnus I (*1 January 1470 – 1 August 1543*)
• Bernard (*? – 1524*), canon in Cologne and Magdeburg
• Eric (*1472–20 October 1522*), as Eric II Prince-Bishop of Hildesheim (1501–1503) and as Eric I Münster (1508–1522)
• John (*1483–20 November 1547*), as John IV Prince-Bishop of Hildesheim (1503–1547)
• Anna von Sachsen-Lauenburg (1468–1504*), ∞ in 1490 John (Johannes Steitz?) of Lindow-Ruppin
• Frederick (*?–before 1501*)
• Rudolph (*?–1503*)
• Henry (died as a child)
• Catherine, Cistercian nun in Reinbek bei Hamburg
• Elisabeth (*1489–1541*), ∞ Duke Henry IV, Duke of Brunswick-Grubenhagen.

One of John V's illegitimate children was:

• Bernhardus Sasse [de] (in Low Saxon, Latin: Bernardus de Saxonia, German: Bernhard von Sachsen; died before 21 February 1549), auxiliary bishop in Münster and titular bishop of Ptolemais in Phoenicia (today's Akko), as of 23 March 1519.