After his father resigned, John V prevailed against his brothers and became
Count of Oldenburg. In his effort to become the ruling count John V invaded the
Weser and
North Sea marshes of
Stadland and
Butjadingen with
mercenaries in April 1499, to both of which the
Prince-Archbishopric of Bremen claimed its
overlordship, in order to subject their free peasants. John had hired parts of the
Black Guard, a
free-lance troop of
mercenaries, commanded by Ulrich von Dornum, who defeated the free peasants in two battles. Already in November
Magnus of Saxe-Lauenburg, then regent in the Land of Hadeln, hired the Black Guard, too expensive for John, in order to conquer the Land of Wursten. Bremen's prince-archbishop
Johann Rode then tried to form a war alliance to repel John's and prevent further invasions, feared for the Land of Wursten, first gaining the cities of
Bremen,
Hamburg and
Stade, which considered the areas downstream the rivers
Elbe and Weser their own front yard existential for their free maritime trade connections. The free peasants in Stadland and Butjadingen liberated themselves from the Oldenburgian yoke in April 1500, supported by
East Frisia. John V could keep his external opponent,
Edzard I, Count of East Frisia in check through alliances. During the
Saxon feud, he and the united Dukes of
Brunswick-Lüneburg attacked Edzard in January 1514. He was then able to conquer Butjadingen and Stadland and parts of the Frisian Wehde. He tried to keep the Stadland area with Esenshamm and Abbehausen as allodial property. However, in 1517, he had to accept them as
fiefs from
Henry V, Duke of Brunswick-Lüneburg. Initially, the dukes of Brunswick occupied Butjadingen. However, after a failed peasants uprising in 1515, they gradually transferred ownership to John V, and by 1523, Butjadingen was definitely owned by Oldenburg. John V died in 1526. After his death, his sons
John VI,
Christopher,
George, and
Anthony I ruled jointly. ==Issue==