Philip IV. of Spain, and the Viceroy of Milan, had raised an army of
14,000 men, intended to act upon the Rhine, independently of
Wallenstein, and to protect Alsace. This force now appeared in Bavaria,
under the command of the Duke of Feria, a Spaniard; and, that they might
be directly employed against the Swedes, Altringer was ordered to join
them with his corps. Upon the first intelligence of their approach,
Horn had summoned to his assistance the Palsgrave of Birkenfeld, from
the Rhine; and being joined by him at Stockach, boldly advanced to meet
the enemy's army of 30,000 men.

The latter had taken the route across the Danube into Swabia, where
Gustavus Horn came so close upon them, that the two armies were only
separated from each other by half a German mile. But, instead of
accepting the offer of battle, the Imperialists moved by the Forest
towns towards Briesgau and Alsace, where they arrived in time to relieve
Breysack, and to arrest the victorious progress of the Rhinegrave, Otto
Louis. The latter had, shortly before, taken the Forest towns, and,
supported by the Palatine of Birkenfeld, who had liberated the Lower
Palatinate and beaten the Duke of Lorraine out of the field, had once
more given the superiority to the Swedish arms in that quarter. He was
now forced to retire before the superior numbers of the enemy; but Horn
and Birkenfeld quickly advanced to his support, and the Imperialists,
after a brief triumph, were again expelled from Alsace. The severity of
the autumn, in which this hapless retreat had to be conducted, proved
fatal to most of the Italians; and their leader, the Duke of Feria, died
of grief at the failure of his enterprise.

In the mean time, Duke Bernard of Weimar had taken up his position on
the Danube, with eighteen regiments of infantry and 140 squadrons of
horse, to cover Franconia, and to watch the movements of the