"...After the fatal battle of Eckmuhl, the Archduke Charles effected, as we have seen, his retreat into the mountainous country of Bohemia, full of defiles, and highly capable of defence, where he could remodel his broken army, receive reinforcements of every kind, and make a protracted defence, should Napoleon press upon him in that direction. But the victories of these memorable five days had placed the French Emperor in full possession of the right bank of the Danube, and of the high road to the city of Vienna, which is situated on the same side of the river. True to his principle of striking directly at the heart of his antagonist, Napoleon determined to march on the metropolis of Austria, instead of pursuing the Archduke into the mountains of Bohemia..."
The second day of the battle of Eckmuhl, on April 22, 1809, turned the War of the Fifth Coalition firmly in Napoleon's favor, in his conflict with Austrian Archduke Charles. Walter Scott notes as much in the passage above, which is taken from his "The Life of Napoleon". Success at Eckmuhl led, ultimately, to the fall of Vienna.