In this paper, we will give an overview of military architecture in the Netherlands, which is very much connected to urban development. Since the late medieval period Holland is the most urbanized region in Europe, with the northern part of Italy. This development started quite recently compared to other European regions, with the construction of earthen walls and wooden palisades around cities. Only from the 13th century onwards, brick was applied as building material for fortifications at a large scale, culminating in the 14th century. Cities were surrounded by high brick walls with towers, which turned obsolete with the introduction of high-power firearms. In the 15th century, Italian engineers introduced new forms of fortification, lowering towers and building the first roundels with gun platforms, which preceded the ever more complex bastioned systems that developed in the early modern period. In the Eighty-Years’ War (1568-1648) against Spain, fortification building reached a new high, both around towns and in the form of ever larger and more elaborate water lines, which were unique for the Netherlands. This system was kept up until the Second World War. During the war, the Dutch coast and especially its urban centres (harbours and industrial areas) were fortified by the Nazis as a part of the Atlantic Wall. In the 19th century many urban fortifications were left to decay or demolished because of the increased range and firepower of attack weapons. After the 1874 Fortification Act (‘Vestingwet’) the defence system was reorganized, with Amsterdam as a national redoubt (‘reduit’) surrounded by water lines with forts. The town fortifications were transformed into urban infrastructure, residential or industrial areas, and greenery, depending on the specific spatial dynamics of each town. The development of the fortified areas depends on the initial situation (landscape, water management and soil conditions), the type of fortification (medieval, medieval with 15th, 16th, and 17th century modifications, ’Old-Netherlandish’, ‘New-Netherlandish’) which also related to situation of towns in relation to historical front lines (Eighty-Years’ War 1568-1648, Franco-Dutch War 1672-1678, &c.), and the specifics of 19th-century urban development (railways, residential demands, industrial areas). The automobile age resulted in ever larger infrastructural works, while at the same time, fortifications were reconstructed as a part of urban identity building. Some fortifications, especially towers, gates and water gates, were repositioned as architectural follies in the new green belts surrounding the cities. Up to now, fortifications were mainly approached from a local point of view; in this paper we will deliver a first comprehensive synthesis of Dutch military architecture.