 Meanwhile, on the 12th U.S. Army Group's southern flank, the 3rd Army had advanced apace, moving eastward to take Erfurt and Weimar, and then, by 12 April, another through the old 1806 Jena Napoleonic battlefield area.On that day, Eisenhower instructed Patton to halt the 3rd Army at the Mulde River, about short of its original objective, Chemnitz.The change resulted from an agreement between the American and Soviet military leadership based on the need to establish a readily identifiable geographical line to avoid accidental clashes between the converging Allied forces.