Wolfenbüttel, occupied by Imperial forces, was a strategically insignificant town, but it held great value to the Swedes' Guelph allies. A Guelph army under
Hans Caspar von Klitzing had blockaded the Imperial garrison under
Johann Ernst, Baron von Ruischenberg since the previous autumn, but its 7,000 troops had been too small a force to reduce the town. Facing growing uncertainty in the wake of the death of General Johan Banér and mutinous troops following a year of inaction and failure, the Swedes needed to do something to ensure Guelph loyalty and prove to other German Protestant allies that they were still a reliable partner. Thus, they decided to assist in the Guelph siege of Wolfenbüttel. Hearing word of the Swedish advance, an Imperial army under Archduke Leopold Wilhelm of Austria and Ottavio Piccolomini raced to meet them.
The race was essentially a draw. The Swedes under Carl Gustaf Wrangel and their Bernardine allies led by French general Jean-Baptiste Budes, Comte de Guébriant joined Klitzing's troops on 28 June, and the Imperial army arrived just two hours later.