By 17 May, the main Austrian army under Charles had arrived on the Marchfeld. Charles kept the bulk of his troops several kilometres away from the river bank in hopes of concentrating them at the point where Napoleon decided to cross. On 21 May, the French made their first major effort to cross the Danube, precipitating the Battle of Aspern-Essling. The Austrians enjoyed a comfortable numerical superiority over the French throughout the battle. On the first day, Charles disposed of 110,000 soldiers against only 31,000 commanded by Napoleon. By the second day, reinforcements had boosted French numbers up to 70,000.