Editing Siege (section)

===New fortresses===
[[File:Atlas Van der Hagen-KW1049B12 098 1-Stadsprofiel van- CANDIA.jpeg|thumb|upright=1.3|The [[siege of Candia]], regarded as one of the longest sieges in history (1648–1669)]]

The most effective way to protect walls against cannon fire proved to be depth (increasing the width of the defenses) and angles (ensuring that attackers could only fire on walls at an oblique angle, not square on). Initially, walls were lowered and backed, in front and behind, with earth. Towers were reformed into triangular bastions.{{sfn|Townshend|2000|p=211}} This design matured into the ''[[trace italienne]]''. [[Star fort|Star-shaped fortresses]] surrounding towns and even cities with outlying defenses proved very difficult to capture, even for a well-equipped army.{{sfn|Townshend|2000|p=212}} Fortresses built in this style throughout the 16th century did not become fully obsolete until the 19th century, and were still in use throughout World War I (though modified for 20th-century warfare). During World War II, ''trace italienne'' fortresses could still present a formidable challenge, for example, in the last days of World War II, during the [[Battle in Berlin]], that saw some of the heaviest urban fighting of the war, the Soviets did not attempt to storm the [[Spandau Citadel]] (built between 1559 and 1594), but chose to [[investment (military)|invest]] it and negotiate its surrender.{{sfn|Beevor|2002|pp=372–375}}

However, the cost of building such vast modern fortifications was incredibly high, and was often too much for individual cities to undertake. Many were bankrupted in the process of building them; others, such as [[Siena]], spent so much money on fortifications that they were unable to maintain their armies properly, and so lost their wars anyway. Nonetheless, innumerable large and impressive fortresses were built throughout northern Italy in the first decades of the 16th century to resist repeated French invasions that became known as the [[Italian Wars]]. Many stand to this day.
[[File:Sitio de Ostende.jpg|thumb|The [[Siege of Ostend]] during the [[Eighty Years' War]], 1601–1604]]
In the 1530s and 1540s, the new style of fortification began to spread out of Italy into the rest of Europe, particularly to France, the Netherlands, and Spain. Italian engineers were in enormous demand throughout Europe, especially in war-torn areas such as the Netherlands, which became dotted by towns encircled in modern fortifications. The densely populated areas of [[Northern Italy]] and the [[Dutch Republic|United Provinces]] (the Netherlands) were infamous for their high degree of fortification of cities. It made campaigns in these areas very hard to successfully conduct, considering even minor cities had to be captured by siege within the span of the campaigning season. In the Dutch case, the possibility of flooding large parts of the land provided an additional obstacle to besiegers, for example at the [[siege of Leiden]]. For many years, defensive and offensive tactics were well balanced, leading to protracted and costly wars such as Europe had never known, involving more and more planning and government involvement. The new fortresses ensured that war rarely extended beyond a series of sieges. Because the new fortresses could easily hold 10,000 men, an attacking army could not ignore a powerfully fortified position without serious risk of counterattack. As a result, virtually all towns had to be taken, and that was usually a long, drawn-out affair, potentially lasting from several months to years, while the members of the town were starved to death. Most battles in this period were between besieging armies and relief columns sent to rescue the besieged.