Read this: While the French army under General MacMahon engaged the German 3rd Army at the Battle of Wörth, the German 1st Army under Steinmetz finished their advance west from Saarbrücken. A patrol from the German 2nd Army under Prince Friedrich Karl of Prussia spotted decoy fires close and Frossard's army farther off on a distant plateau south of the town of Spicheren, and took this as a sign of Frossard's retreat. Ignoring Moltke's plan again, both German armies attacked Frossard's French 2nd Corps, fortified between Spicheren and Forbach.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): Which German divisison did MacMahon engage?
German 3rd Army