The battle of Vitebsk (28 July 1812) was one of Napoleon's great missed chances during his invasion of Russia of 1812. By delaying his attack for a day he missed an opportunity to fight a major battle against Barclay de Tolly's 1st Western Army and allowed the Russians to slip away.
For the first two weeks after the start of the invasion Napoleon focused most of his efforts on an attempt to trap General Bagration's 2nd Western Army, on the left of the main Russian line. By 8 July these efforts had failed and Bagration had slipped away to the east. Davout was sent to shadow Bagration and prevent him from moving north to join Barclay de Tolly, while the main part of Napoleon's army turned north. At this point Barclay de Tolly's army was in the fortified camp at Drissa on the Dvina River, but the Russians soon realised that this position was indefensible and on 19 July Murat reported that the Russians had abandoned the camp and were heading east.
Napoleon's first instinct was that Russians were heading for Polotsk, and he ordered his army to concentrate to the south-east of that town in an attempt to cut off the Russian retreat. By 21 July Napoleon realised that he was mistaken and the Russians were instead heading further east to Vitebsk. He ordered his men to move further east and by 24 July they had reached Biechenkowski, on the south bank of the Dvina, west of Vitebsk.
At this stage Barclay de Tolly was intending to stand and fight at Vitebsk. He believed that Bagration was approaching from the south, and decided to try and delay the French until the two Russian armies had united. On 23 July Bagration's men attacked Davout at Mogilev on the Dnieper, but were repulsed. This meant that Bagration would have to cross the river further south and to head towards Smolensk. When this news reached Barclay de Tolly he would abandon his plans to fight and join the retreat to Smolensk, but for the moment Napoleon had the chance he needed.
The French began to advance east on the night of 24-25 July. They ran into the Russian rearguard at Ostronovo and a two-day battle began (25-26 July). The Russians were able to delay the French, but by the end of 26 July they had pulled back to Vitebsk.
At dawn on 27 July Napoleon was finally where he wanted to be, with a Russian army preparing to fight, but he then made a fateful decision. Instead of attacking immediately with the troops at his disposal he decided to wait for a day to give him a more overwhelming advantage. During the day a messenger reached Barclay de Tolly from Bagration announcing his enforced change of route. There was now no point fighting at Vitebsk, and so on the night of 27-28 July the Russians abandoned the city and began a retreat towards Smolensk .
Dawn broke at about 4am on the morning of 28 July, and the French received a massive shock. The Russian army that they had been facing across a small stream on the previous night had gone. Napoleon entered the almost deserted town at 10am and discovered that most of the 20,000 inhabitants had also left.
The only fighting on the day that might have seen the first major battle of the campaign was a series of limited rearguard actions fought between the leading elements of Murat's cavalry and the Russian rearguard. Napoleon was forced to stop and allow his men to rest, and for the next week the infantry recuperated around Vitebsk while Napoleon decided what to do next. When he finally decided to move it would be east, towards Smolensk and another chance at a major battle.