Between roughly 200 and 450 CE, this water was a place of offering. When an army was beaten, the victors gathered up what the losers had carried — swords, lances, spears, bows, arrows, round shields, belt buckles, brooches, ornate clasps — and destroyed it before committing it to the bog. Blades were bent double. Shafts were snapped. Shields were hacked apart. The point was not disposal but dedication: the equipment was given to the gods in thanks, and giving it meant making it useless to anyone living. Nothing here was lost. Everything was put here on purpose, by people performing a rite whose logic they understood completely and we can only reconstruct.

The archaeologist Conrad Engelhardt worked the bog from 1859 to 1863 and found the deposit largely as it had been left. Alongside weapons, tools and fragments of clothing lay two intact clinker-built boats, one of oak and one of pine, with the remains of a third beneath them — that one apparently broken up as part of the sacrifice itself. On 17 August 1863 he uncovered the largest of them. The oak boat measured about 23 metres long and roughly 3.5 metres in the beam, weighed over three tonnes, and carried fourteen pairs of oars for a crew of perhaps forty-five men. Dendrochronology later dated its timbers to 310–320 CE.

Engelhardt's excavation stopped in early 1864 when the Second Schleswig War broke out a few kilometres away, and the war then consumed part of what he had recovered. The pine boat, perhaps nineteen metres long, was chopped up by troops and burned for firewood. When Denmark lost the war and the territory around the bog with it, the oak boat was handed over to Prussia. It is still in Germany, displayed at the archaeological museum in Gottorf Castle in Schleswig. Older Danish vessels exist — the Hjortspring boat predates it — but the Nydam oak boat remains one of the oldest known rowing ships from northern Europe, and one of the few large objects a border war carried off intact.

Local interest in Nydam never faded, partly because the finds sit precisely on the fault line between Danish and German culture in the borderland. The Society for Nydam Research — the Nydam Society — formed in 1983 and pressed for the site to be examined again. The National Museum of Denmark resumed excavation in 1989 and pulled out a further large body of material: more swords, spears, bows and arrows, and the small personal things that armies carry, dated across the period 250–550 CE. The society also built what it had wanted for decades. Nydam Tveir, a full replica of the oak boat, was constructed using the tools and techniques of the period, in two phases — a feasibility study first, to learn how such a hull could be worked at all, then the boat itself.

Nothing about the place announces itself now. Park on Nydamvej, take the path called Nydamstien, and about ten minutes' walk brings you to a small white building, Nydamhuset, beside a quiet field. The bog has become a meadow. Standing at the edge of it, the scale is hard to hold: somewhere under that grass, a warship the length of a tennis court was rowed or dragged in, filled with the ruined arms of a defeated enemy, and pushed under the water as a gift.