Historians of the Eighty Years' War call Maurice's 1597 campaign part of the Ten Glory Years - a stretch when the young Dutch Republic, organized and disciplined under Maurice and his cousin William Louis, took back city after city from Habsburg Spain. Maurice was not a romantic figure. He was an organizer. He drilled his soldiers to load and fire on count, paid them on time, kept his siege artillery well maintained, and moved fast enough that his opponents were often still arguing about how to respond when he arrived. The 1597 eastern campaign was textbook Maurice: pick the weak Spanish garrisons one at a time, surround them with overwhelming force, demand surrender on terms that allowed an honorable march out, and move on before the enemy could concentrate a relief army.

Oldenzaal had been Spanish since 1572 - twenty-five years - and the city was deeply Catholic in a country whose new ruling class was Calvinist. Every year the Spanish garrison and the local clergy held a procession celebrating the expulsion of the Beggars, the loose name for the Dutch rebels who had tried and failed to take the city earlier in the war. The defensive works, when Maurice arrived, were not nothing: a main wall, six bastions, a moat, an earthen rampart. But the rebuilding work had stalled, and parts of the defenses were unfinished. Six companies of 400 men with one large gun could in theory hold out for weeks against a poorly equipped attacker. Against the Dutch and English siege train, they could not.

Frederick Boymer was an experienced commander, and he understood the script. In seventeenth-century siege warfare, a garrison that resisted long enough to demonstrate good faith - but surrendered before the besieging army stormed the walls - could expect honorable terms. Storm a city and the rules of war permitted sacking it; capitulate in time and the defenders marched out with their personal weapons, sometimes with drums beating and banners displayed, free to rejoin their main army. Boymer waited four days. Then he opened negotiations. The terms were signed with the governor and the local clergy together - a recognition that the Catholic Church inside Oldenzaal had an interest in the outcome as much as the soldiers did - and on 24 October the Spanish garrison marched east to Lingen with full honors. The clergy stayed. Many of them would not have a pleasant time under the new regime, but no one was killed.

Oldenzaal in 1597 was a small Hanseatic city, the kind of place Maurice's troops had liberated dozens of times: a parish church at the center - in this case the Sint-Plechelmusbasiliek, already four centuries old - surrounded by the houses of merchants and craftsmen, ringed by the walls the Spanish had been trying to improve. Maurice's first acts on entering a city were usually the same. Confirm civic privileges. Secure church buildings. Install a Protestant minister where the law required it. Set up provisioning for his troops. He was not a religious zealot by the standards of his era, but the Dutch Republic was officially Reformed, and the public face of a captured Catholic city had to change. Mass continued in private for some time. The basilica eventually became a Protestant church and would only be returned to Catholic use centuries later.

Oldenzaal did not stay Dutch in 1597. The Eighty Years' War rolled on, and in 1605 the Spanish general Ambrogio Spinola - one of the few commanders the Dutch genuinely feared - captured the city back. It took another twenty-one years before Frederick Henry, Maurice's half-brother and successor as stadholder, retook Oldenzaal in 1626. From that point on it stayed permanently in Dutch hands. The four-day siege of 1597 was not the final word, but it was a clear early sign of what the disciplined Dutch military machine could now do. The Republic's independence would not be formally recognized until the Treaty of Munster in 1648 - fifty-one years after Maurice's troops marched through Oldenzaal's gates - but the contours of the country that would emerge were already taking shape in campaigns like this one.