To build on what some others have pointed out:

He would divide his forces into smaller units. This would allow them to cover more territory/ strategic points. This gives you multiple places to defend against any enemy strikes as well as allows you to forage for food a lot easier, as feeding 500 men in ten different cities is much easier than feeding 5000 men in one city.

You might think that defending multiple fronts is terrible, and you'd be right, but the enemy would do the same thing to counter your armies from encircling them. If they didn't split their forces, then you would possibly disrupt their own supply lines or take vital cities.

If they did split their forces, Napoleon would then gather up most of his forces from each of his different parts of his army, march them through the night or through the early morning, and then attack the divided enemy forces. Once a majority of the enemy was routed, he would go back and try and save all the smaller skeleton crews he had left behind to stall the enemy from uniting his forces.

He would do this while adding in some truly ingenious artillery and infantry tactics. His cavalry tactics weren't great, but he had a lot of great cavalry generals help him with those tactics (as well as great infantry and artillery generals). His generals were generally better than their counterparts in opposing armies, too. This is because they were not only getting a lot of experience in fighting, but also Napoleon started building his officers out of a meritocracy and not a monarchy's lords and nobles.