Charles John, as the Commander-in-Chief of the Northern Army, successfully defended the approaches to Berlin and was victorious in battle against Oudinot in August and against Ney in September at the Battles of Großbeeren and Dennewitz. Bernadotte's Army of the North would continue to guard Berlin and keep watch on Davout's forces in Hamburg while the Allies, in accordance with the plan conceived at Trachenberg, maneuvered toward Napoleon's army at Leipzig. With the other Allied armies engaged in battle on 17 October, Bernadotte's army finally crossed the Elbe and joined in the Battle of Leipzig on 19 October. His fresh troops, reinforced by 30,000 Prussians, joined the fray against the already battered French lines where Swedish forces entered battle in numbers for the first time in the campaign. At a critical moment entire Saxon regiments went over to his army in response to a proclamation released a week prior in which Bernadotte invited the Saxons to join their old commander in defeating Napoleon. The Army of the North committed the "coup de grâce" on the already depleted French and Bernadotte was the first of the Allied sovereigns to enter Leipzig.