[1] In April 1646, Carl Gustaf Wrangel, the appointed successor of Lennart Torstensson as overall commander of all Swedish forces in Germany, marched into Westphalia to get closer to the French army.

[1] Torstensson had been allowed to return home, but not to retire, as several senior leaders along with Axel Oxenstierna and the Queen regularly spoke to him about German affairs.

[4] At the end of June, Leopold William's Imperials supported by 6,900 Bavarians under Gottfried Huyn von Geleen set up camp at Homberg (Ohm) with the intention of preventing the conjunction of Sweden and France.

Seeing this, the Imperial troops did not risk to storm the Swedish position and pulled back in late July when an epidemic began to rage among their horses.

[2] The Imperial-Bavarian army tried to stop them with entrenchments along the Main and Nidda rivers but the Swedes and French simply bypassed the defences and moved on to the Danube via Heilbronn.

However, with news of an approaching Imperial army under the command of the Archduke Leopold William reaching both Wrangel and Turenne, they quickly decided to abandon the siege after a failed storm.

[8] Turenne and the French army would then depart and establish winter quarters around Donau in Swabia, with Wrangel going to the lands around Lake Constance on the Swiss border, whose countryside had not been plundered yet.

[4] Swedish patrols had told Wrangel about the vulnerability of the city of Bregenz at the eastern end of the lake where the surrounding population had put their valuables.

Wrangel would then claim the title "Admiral of Lake Constance" which was likely a mocking retaliation for the appointment of Wallenstein as "General of the Oceanic and Baltic Seas" in 1628.