Rudolf I of Germany
Rudolf I declares war on Ottokar II of Bohemia
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Original prompt & settings (JSON) ↗Rudolf declared war on midsummer day but waited until mid-August to leave the Rhine, using the interval to peel away Ottokar's allies.
24 June 1276
On 24 June 1276, King Rudolf I formally declared war on King Ottokar II of Bohemia.
He simultaneously renewed or intensified the imperial outlawry directed against Ottokar and his supporters; an initial imperial ban had been in place by 1275 and had not compelled compliance.
Ottokar had refused to recognise Rudolf's election, answer imperial summons, or surrender territories that Rudolf and the princes judged reverted to the imperial crown.
A declaration, not a march
The declaration converted a long-running legal dispute over Ottokar's recognition of Rudolf and possession of imperial fiefs into an announced military conflict. Rudolf did not begin his principal advance that same day.
He left the Rhine region in August, and one scholarly chronology dates the active Austrian campaign from late September.
Ottokar prepared for an invasion of Bohemia; Rudolf instead pivoted south after Henry XIII of Lower Bavaria changed sides, and advanced toward Vienna.
Vienna by November
Allied advances and defections isolated Ottokar. Meinhard II of Gorizia-Tyrol helped bring Carinthia and Styria onto Rudolf's side, and Vienna was besieged.
The settlement came in several connected acts: an arbitral settlement dated 21 November, and the preliminary peace instrument that the Austrian State Archives identifies as 26 November 1276.
The peace was reinforced by planned marriages between the two royal families only months after they had gone to war.
Sources
Researched 24 Aug 2026 6 sources not yet audited Date corrected
How this was checked
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Date corrected. The research places this at 1276-06-24.
What the sources leave uncertain
- The precise legal sequence is sometimes compressed: Ottokar was placed under an initial imperial ban by 1275, while 24 June 1276 brought the declaration of war and a renewed or aggravated ban.
- The peace settlement existed in several connected acts. An arbitral settlement is dated 21 November, while the Austrian State Archives identifies the surviving preliminary peace instrument as 26 November 1276.