There was still one chance to achieve an early blow against the Russians and Napoleon ordered Davout to take his corps to intercept Bagration, while Jérôme pursued him from the south. Then in early July, while Napoleon waited at Vilna for news of the positions of the Russian armies, Berthier brought him a despatch from Jérôme.

‘What does my brother have to say?’ Napoleon asked as he lay in a bath in the town’s finest hotel.

Berthier scanned the report and then looked up nervously. ‘Sire, Jérôme says that his cavalry patrols lost contact with the Russians two days ago, on the third.’

Napoleon sat up. ‘Lost contact? How can they lose contact? Where is Jérôme?’

‘The despatch was sent from Grodno, sire.’

‘Grodno?’ Napoleon recalled the name from the map and his brow knitted angrily.‘What the hell is Jérôme doing? Why is his army moving so slowly? That young fool is going to cost us dear. Berthier, take this down. Tell him that it would be impossible to lead his men in a worse manner. He should have been harassing Bagration at every step. Then he might have driven the Russians into Davout’s path. We could have crushed one of the Tsar’s armies. Instead he has let it escape. You tell him that he has robbed me of all that I had hoped to achieve. We have lost the best opportunity ever presented in this war, all because he has failed to learn the most fundamental principles of warfare. Did you get all that?’

‘Yes, sire.’

‘Send it at once. With luck that might spur the fool into activity. Too late to do much good now, though. Let’s hope he responds with greater alacrity next time.’

There was not to be a next time. The next despatch from Jérôme’s headquarters was written by Marshal Davout. The Emperor’s letter had caused his younger brother so much offence that he had abandoned the army to return to his kingdom of Westphalia, leaving Davout to assume temporary command of his corps. Despite his anger, Napoleon considered the news a blessing of sorts as he continued his pursuit of the main Russian army.

July brought with it several days of rainstorms that lashed the columns of the Grand Army as it tramped eastwards, driven on by its commander in his desire to find the Tsar and his soldiers and bring them to battle. Within hours every rutted track was turned into a muddy morass that sucked at the boots of the men and the horses’ hooves and slowed the speed of the artillery trains and supply wagons to a crawl. The Emperor’s marshals, aware of his orders to press on at all costs, left a small guard behind to escort the wagons and continued the advance.