Johan Maurits van Nassau was not a frontline warship. Built in Vlissingen and commissioned in 1932, she was a coastal gunboat, designed for fisheries protection and showing the flag in the Dutch East Indies and the West Indies. Her three 5.9-inch guns were respectable but not heavy; her speed was moderate; her armour was light. She was, however, fitted with a fire-control system more advanced than her size suggested - a piece of equipment that would matter more than her builders could have known. When war broke out in September 1939 she was on station in the West Indies. The Netherlands intended to relieve her with a new training ship and bring her home. The relief was delayed. By the time she finally reached Dutch waters, the Germans were two days from invasion.

On 10 May 1940 she was anchored at Vlissingen, watching the southern approaches. The day the Germans came across the border she was already at action stations, and within hours she had shot down one of the aircraft that came for her. Ordered north to bombard Waalhaven aerodrome at Rotterdam - paratroopers had seized it on the first day - she made it as far as Hook of Holland before the destroyer Van Galen, attempting the same mission, was lost. The order was cancelled. She turned back, then was redirected to Den Helder to join the defense of the northern coast against advancing German forces along the Afsluitdijk.

On 14 May she went to work. The Germans had positioned 88 mm guns of the 1st Kavalleriedivision near the eastern end of the Afsluitdijk, the long causeway sealing the IJsselmeer from the North Sea, and the battery commanded approaches the Dutch needed to keep open. Johan Maurits van Nassau took position eighteen kilometers offshore and opened fire. Her advanced fire-control system delivered accuracy that her displacement should not have allowed. The German guns were silenced. German aircraft attacked her in retaliation through the morning and into the afternoon; she absorbed the attacks and kept firing. By the time the engagement ended she was still afloat, still on station, and her crew - to their own astonishment - was unhurt.

Hours later the war in the Netherlands was effectively over. Rotterdam had been bombed the day before. The general evacuation was underway. Johan Maurits van Nassau left Den Helder in the afternoon convoy bound for England, the largest vessel in a small group of ships hoping to slip past German air patrols. About sixteen kilometers west of Callantsoog the Luftwaffe found them. She took two or three direct hits. One of them started a fire near an ammunition magazine. The captain ordered abandon ship. Seventeen crewmen did not make it off - sailors who had survived the first morning of the invasion, survived the bombardment at the Afsluitdijk, and survived everything except this last afternoon at sea. The rescue ship Dorus Rijkers gathered most of the survivors and brought them back to Den Helder. Some of those who lived continued on to England aboard the rest of the convoy.

Her wreck still lies in twenty meters of water off the North Holland coast, roughly halfway between Den Helder and Callantsoog. It is a maritime grave by Dutch designation - the seventeen who died abandoning ship are presumed to be there with her. From altitude on a calm day the position shows as a faint dark patch on otherwise even water, depending on tide and weather. Among the categories Wikipedia files her under - 1932 ships, ships sunk by German aircraft, gunboats sunk by aircraft - one phrase repeats in the documents: maritime incidents in May 1940. It is a clean military formulation for a small ship that did very nearly everything asked of her, against odds that should have stopped her earlier, before the run for England that turned out to be a run she could not finish.