For two weeks the Danish army under General Christian Julius de Meza had held the Dannevirke, the ancient earthwork line drawn across the neck of Schleswig, and on 2 February it turned the Prussians back at Mysunde. Two days later the Prussians crossed the Schlei anyway, and the shape of the campaign changed: the Danes were about to be encircled in a position they lacked the heavy artillery to defend. De Meza chose the army over the symbol. On 4 February the withdrawal toward the redoubts at Dybbøl began, through freezing weather and, at its worst, a snowstorm — which at least slowed the pursuit. Austrian troops under Ludwig von Gablenz came after them regardless, and the Danish 7th Brigade was ordered to stop them.

The brigade was two regiments and very little else: the 1st, made up of men from Copenhagen, and the 11th, drawn from Vendsyssel at the northern tip of Jutland. City and countryside, put down side by side on either side of the highway between Sankelmark and Oeversee, with perhaps two field guns against the Austrians' eight. Gablenz had the numbers. Müller went first anyway, sending the 1st Regiment forward around half past three. The Danes came on with bayonets, and against the arithmetic they stopped the Austrian advance where it stood.

What followed was close and ugly — hand-to-hand in places, neither side able to break the other, for the better part of an hour and a half. At about five o'clock, as the sun went down, an Austrian bayonet charge finally pushed the Danes off their ground. The 7th Brigade fell back and rejoined the main army, and Austrian gunners found the column as it withdrew; a considerable share of the day's losses came in that last open stretch.

Both armies counted, and disagreed. The Danish accounting records 53 Danes killed, 157 wounded and 553 taken prisoner, against 95 Austrians killed, 311 wounded and 27 missing. The Austrian accounting puts Danish losses at 962 and its own at 431. Whichever set of figures you accept, several hundred young men from Copenhagen tenements, Jutland farms and the towns of the Habsburg empire spent that night lying in a Schleswig field in February.

Militarily it worked. The pursuit was blunted and the Danish army reached Dybbøl intact on 7 February. In Denmark it was received as a disgrace. Victory in the First Schleswig War had left the country convinced of its own military superiority, and the Dannevirke — the old frontier between Danes and Germans — had become a sacred object rather than a line to be soberly assessed. Only the army seemed to grasp that it could not be held. De Meza, who had just saved his force from destruction, was dismissed by the Minister of War, and Denmark lost one of its ablest commanders at the worst possible moment. It lost something else too: after the outcry, no government could contemplate a second withdrawal. The army had to stand at Dybbøl, and in April it was broken there.

The morning after the fighting, people came out from Flensburg, about ten kilometres up the same road, to help the wounded — Danish and Austrian alike, lying where the day had left them. That is what the place still commemorates. An Austrian memorial stands at Oeversee, and every year a march sets out from Flensburg-Martinsberg toward the battlefield, remembering not the charge or the bayonets but the townspeople who walked south the next morning with whatever they had. Sankelmark today is a quiet lake and a stretch of road between fields. It takes a memorial and a footpath full of walkers in February to say what happened here.