The Zijpe polder was not a battlefield. It was a piece of seventeenth-century engineering - a former marsh embanked into farmland in the 1500s - that happened, by accident of geometry, to be one of the strongest defensive positions in Europe. Its southern dike rose high above the surrounding country. A wide, deep drainage canal ran along it like a moat. The dike was not straight; it jogged in and out at intervals, producing angular projections that let defenders pour enfilade fire along its length, the way a trace italienne fortress did. The British general Ralph Abercromby took one look and recognized what he had. He anchored his right flank on a subsidiary dike near Petten, ran his line east through the villages of Krabbendam, Eenigenburg, and Sint Maarten, and ended it at the Oude Sluys on the Zuiderzee shore. He added artillery positions and earthworks where the natural cover did not suffice. By the time Brune was ready to attack, Abercromby had built a fortress out of farmland.

Brune intended a single envelopment. The Batavian divisions under Daendels would press the British line frontally at Eenigenburg and Krabbendam, pinning Abercromby in place. The main blow would be delivered on the French left, where Dominique Vandamme's division would advance up the subsidiary dike near Petten and turn the British right. The plan looked clean on paper. The plan was a paper plan. Brune knew that British and Russian reinforcements were a few days away - already 40,000 men were forming up behind Abercromby - and so he committed to the attack before his own staff had finished its work. Reconnaissance was sketchy. The maps were misread. The orders went out anyway.

The first thing that went wrong was a routing error. Two columns - Daendels' from St. Pancras and one of Dumonceau's - were ordered down the same road. Except it was not a road; it was a canal. Someone on Brune's staff had read the map wrong and assigned a watercourse as a march route. Daendels had to swing east on a different track and shift his objective from Eenigenburg to Sint Maarten, which he duly took without much resistance. The second thing that went wrong was Colonel Bruce. He was supposed to advance on Krabbendam from Alkmaar, but the city gate he needed to use was blocked by a long line of farmer's carts heading to market. He sat there until they cleared. He did not arrive at his starting position until seven in the morning - hours late, after his support and his attack had already lost their synchronization.

On the French left, Vandamme advanced his division up the sea dike and the subsidiary dike at Petten, into the teeth of the British sconce at the head of the line. The French grenadiers were brave. They closed under fire and pressed all the way to the great ring canal at the foot of the Zijpe dike. There the polder geometry caught them. The canal was deep, wide, and cold, and the men trying to cross it under fire from the British defenses on the high bank had no good way to get across. Many drowned in their kit, dragged down by waterlogged uniforms and equipment. General David was among them - a French general killed not by a musket ball but by a polder drainage ditch designed two centuries earlier to keep cows in their fields. When four British gunboats slipped close inshore and began firing on Vandamme's flank, the attack collapsed. Vandamme fell back to where he had started.

In the center, the impatient General Dumonceau borrowed a hundred grenadiers from General Bonhomme's column and threw them at Krabbendam himself. To everyone's surprise, including his own, they took the village. The British counter-attacked. Dumonceau took it a second time. Two battalions of the 20th Foot under Lieutenant-Colonel Smyth and Major Ross drove him out again, this time for good. By three in the afternoon he had withdrawn to Schoorldam, and the battle was over. The accounting was brutal: 1,876 Franco-Batavian dead and wounded against 184 British. That night a false rumor of a British attack started a panic in Daendels' camp. Some of his troops bolted as far as Haarlem before they were stopped. Brune, the Wikipedia article notes drily, was not amused. Nine days later the Duke of York, now in supreme command of the swelling Anglo-Russian force, broke out of the Zijpe at the Battle of Bergen. The campaign would not turn against him for another five weeks - long enough to make Krabbendam look, in hindsight, like the moment when stopping the invasion still might have been possible, if only someone had read the map.