Napoleon defeated Prince Gebhardt von Blücher’s Army of Silesia at the Battles of Champaubert, Montmirail, Château-Thierry and Vauchamps between 10 and 14 February 1814. However, Prince Karl Phillip zu Schwarzenberg’s Army of Bohemia had taken the offensive in the Seine sector.
Napoleon’s original plan had been to attack Schwarzenberg’s lines of communication once he had dealt with Blücher. However,. By 15 February it was clear that the French forces facing Schwarzenberg would not be able to hold his advance on Paris for the two to three days that this manoeuvre would take to organise. David Chandler points out that Napoleon ‘could not ignore a direct threat to Paris, and consequently had to adopt a less decisive plan.’
Click here for a campaign map from West Point’s website and here for a map of the Battle of Montereau.
Napoleon left the corps of Marshals Édouard Mortier and Auguste de Marmont to cover Paris in case Blücher resumed the offensive. He took the Imperial Guard and General Emmanuel de Grouchy’s cavalry 47 miles south in 36 hours, with some of his infantry travelling in wagons and carts. He entered Gugnes at 3pm on 16 February.
Including the troops that were already in the Seine sector, Napoleon now had 60,000 men with which to attack the Army of Bohemia. He was heavily outnumbered, but Schwarzenberg’s four corps were widely spread. General Friedrich von Bianchi’s Austrians, General Karl Phillip von Wrede’s Bavarians, Prince Ludwig Pyotr Wittgenstein’s Russians and the Württembergers under their Crown Prince, were advancing along separate roads. Poor connecting roads, mud and the Seine made it hard for them to stay in contact with each other.
Wittgenstein, on the Coalition right (northern) flank had pushed on ahead of the rest of the Army of Bohemia. On 17 February its 4,300 strong advance guard, under General Pyotr Pahlen, was overwhelmed at Mormant by Napoleon’s advance guard, commanded by General Maurice-Etienne Gérard, with supported from Grouchy. Gérard and Grouchy then forced Wrede’s advance guard to retreat from Valjouan. 
Marshal Claude Victor’s corps was supposed to have taken part in these two actions, but moved slowly. Victor, Gérard and Grouchy, along with General Claude-Pierre Pajol’s cavalry, were then ordered to advance quickly to Montereau. Napoleon wanted to beat the retreating Army of Bohemia to Troyes.
Victor had been ordered to reach Montereau at 6 am on 18 February, but paused overnight, allowing the Württembergers time to prepare their defensive position. The first French troops to arrive were 1,500 cavalry, 3,000 National Guards and 800 gendarmes under Pajol. They were poorly trained, and were unable to make any progress against the Württemberg corps of 8,500 infantry, 1000 cavalry and 26 guns.
Victor’s advance guard did not arrive until 9 am. His initial attacks were unsuccessful. Napoleon, angry at his tardiness, replaced him with Gérard. Napoleon and the Guard arrived at 3 pm. The French now had 30,000 men and 70 guns on the field, and the Württembergers withdrew in the face of new attacks. They lost 5-6,000 men, 3,400 of them being captured, and 15 guns. French casualties were 2,500 killed and wounded.
The defenders had the Seine behind them, with only one bridge to retreat across. A final French cavalry charge, in which Pajol was so severely wounded that he took no further part in the war, captured both the Seine bridge and one over the Yonne before the Württembergers could blow them. F. Loraine Petre suggests that they should have retreated and destroyed the Seine bridge as soon as they were attacked, but Schwarzenberg had ordered them not to do so.
On the same day the French reached the Seine at Nogent and Bray, only to find the bridges had been blown. As they then had no bridging train, the capture of the bridge at Montereau was vital. They also took a bridge over the Yonne as after the battle of Montereau.
Schwarzenberg now ordered his army to retreat to Troyes, less Wittgenstein’s corps, which was to link up with Blücher at Méry by 21 February. Napoleon, who now had 75,000 men with him, pursued rapidly with the intention of fighting Schwarzenberg near Troyes on 23 February. Schwarzenberg had 90,000 troops and Blücher 50,000. However, Alexander Seslavin, a Cossack commander regarded as ‘very reliable’ by his superiors, had reported that Napoleon now had 180,000 men.
Petre notes that Schwarzenberg was worried about ‘the incalculable results of defeat.’ He was also concerned by the threat to his line of retreat of from Marshal Pierre Augereau’s corps in the south, ‘unnecessarily’ according to Chandler. Schwarzenberg therefore decided to withdraw his army to Troyes. He ordered Blücher to retreat his army, including Wittgenstein’s corps, across the Marne.
Chandler contends that ‘Schwarzenberg’s inglorious but probably justifiable caution thwarted Napoleon of a decisive action.’ He goes on to argue that the Emperor had outmanoeuvred and outfought two enemy armies that both outnumbered him, but could not win a military victory because he lacked the necessary manpower and France was war-weary.
Napoleon could probably have now agreed a peace settlement that would have left him Emperor of France within its 1792 borders. He had reluctantly allowed his foreign minister, the Marquis de Caulaincourt, to negotiate on that basis after his defeat at La Rothière on 1 February. However, his subsequent victories meant that he was prepared to accept nothing less than France’s natural frontiers, stretching to the Rhine, and perhaps even wanted to keep Italy. He told his brother Joseph that:
If I had accepted the historical borders I would have taken up arms again two years later, and I would have said to the nation that this was not a peace that I had signed but a forced capitulation.
 D. Chandler, The Campaigns of Napoleon (London: Weidenfeld & Nicolson, 1966), p. 978.
 Troop strengths in this and the previous paragraph are from are from Ibid.
 French casualties are from Ibid., p. 980, which says that Württemberg casualties were 6,000. Other numbers in the last two paragraphs are from F. L. Petre, Napoleon at Bay 1814 (London: John Lane, The Bodley Head, 1914), pp. 83-85.
 Ibid., p. 85.
 Ibid., p. 88.
 Ibid., p. 89.
 Chandler, Campaigns, p. 981.
 Ibid., p. 982.
 Quoted in D. C. B. Lieven, Russia against Napoleon: The Battle for Europe, 1807 to 1814 (London: Penguin, 2010), p. 490.