One of the characteristics of urban warfare during the ancient period that still holds true in modern operations is the issue of time. Ancient commanders realized that there were essentially two approaches to urban warfare. One approach was a quick, decisive action to capture the city. This could be accomplished by deploying the main force of the army before the city could be prepared for defense; or, it could be accomplished by deceit. Often allies within the city might be persuaded to compromise the city’s defenses.
The ancients demonstrated another characteristic of urban fighting that has remained consistent through history: the burden borne by the civilian population. Unlike open battle, where the civilian population had little direct experience of the operation and only indirect experience of the consequences, the civilian population of an urban area involved in battle was directly involved in both the operation and its consequences. This characteristic of urban combat remains valid into the 21st century. Civilian casualties in city battles could be extraordinarily high. At both Tyre and Jerusalem, after the battle the entire city populations were either killed or enslaved.
The importance of urban operations did not abate in the Middle Ages. Medieval warfare revolved around campaigns designed to capture cities. Attack techniques remained relatively consistent with ancient practices. One of the most successful warrior kings of the period, Henry V of England, famous for his battlefield victory at Agincourt, conducted many more sieges than battles, and they were much more decisive in his campaigns against France. His two-year siege of Rouen, 1417–19, demonstrated how urban warfare in the medieval period was often time consuming, and the death from starvation of many women and children within the city demonstrated that fighting for cities was as brutal as ever.
As Europe entered the Renaissance, an age of scientific discovery, explorations, and invention, combat to control cities remained as critical as ever to warfare. The invention of gunpowder did not change the centrality of cities to warfare but it did change the design of cities. Ancient and medieval cities were typically surrounded by high vertical walls which forced attackers to tunnel underneath, or use towers or ladders to climb over them. Gunpowder and cannon made quick and easy work of vertical stone walls, and cities responded by lowering and widening the walls. The invention of artillery was one of the most important weapon advances in military history and was a direct response to urban fortification. Artillery was initially designed specifically to deal with the walls of medieval castles and walled cities. It was so effective that it quickly caused the demise of the castle and resulted in drastic changes in the design of fortified cities. Large numbers of artillery pieces were used to attack cities. However, artillery was not normally used against the city itself. The primary purpose of artillery was to create a breach in the surrounding wall. Secondly, artillery was used to suppress enemy fire, including enemy artillery, during the approach to the walls of the city and the final assault through and over the city walls. Artillery was not commonly used against the population or structures of a city unless a commander specifically decided to compel the city’s surrender through bombardment.
Engineers remained at the forefront of siege warfare and led the response to the new gunpowder technology. Cities lowered their walls and backed the stone fronts with thick earthen embankments. Defenders mounted their own cannon on the wide top of the walls. The engineers carefully designed the trace of the walls so that each wall front was enfiladed by cannon firing from walls on its flank. The resulting design resembled a star and for several hundred years many of the major cities of Europe were surrounded by star fortifications. Engineers in the early modern period were also responsible for designing assaults on fortified cities. Engineers evaluated the defenses, carefully studying distances, angles, outlying fortifications, the thickness of walls, and lie of the surrounding terrain. Based on this, the engineer designed the siege assault plan. The generals commanding the troops made all the command decisions, but those decisions were based on the recommendations of the engineer.
The most famous engineer of this era was Sebastien Le Prestre de Vauban, the chief engineer for Louis XIV of France. Vauban was commissioned as an engineer lieutenant in 1755 and by 1759 he had participated in ten major siege operations. In subsequent years he supervised the successful assault on over 20 cities. He was an expert in both the attack on and the building of fortifications. In his career he improved the fortifications of over 300 cities and supervised the building of 37 new fortresses. His greatest contribution to the art of city combat was the creation of a formal siege methodology. His methodology consisted of choosing the point of attack; emplacing long-range artillery; building a series of protected approach trenches; emplacing close artillery batteries; building more covered trenches to approach the wall of the city; and then, once the supporting artillery silenced defending artillery and created a breach, the infantry assaulted the city’s defensive wall from the cover of the approach trenches. Vauban’s siege tactics remained the standard for attacking a city almost until the 20th century.
Engineers supervised two types of specialty troops necessary for urban operations: sappers and miners. The engineers generally had exclusive control of the use of miners but had to share the direction of sappers with the artillery. Often this unclear chain of command caused delays in the execution of siege operations. Sapping, the digging of trenches under almost constant fire, was extremely dangerous work. Vauban instituted a system of cash rewards based on progress and danger. With these incentives, Vauban’s sappers could complete 480 feet of trench every 24 hours.
Mining remained an essential element as long as cities were defended by prepared positions and fortresses. Mining could take one of two forms. In one form, a deep mine was started well outside the fortification and dug to its foundation. Barrels of explosives were then positioned against the foundation and detonated. The result, if done properly, was the destruction of the wall and the creation of a huge crater, which became the entry point of the following infantry assault on the city. The other type of mining was called “attaching the miner.” This technique was a direct mine into the base of the fortress wall. The miners quickly burrowed directly into the base of the wall as the enemy above was suppressed by fire. The miners then branched left or right under the wall. Once properly positioned, explosives were placed in the mine under the wall, and detonated, bringing down a section of wall. The infantry assault then entered the city over the rubble resulting from the collapsed wall. Mining was often used when artillery proved ineffective. Engineers, sappers, and miners were absolutely critical to successful siege operations. There were never enough of them, and delays ensued when engineers were not present, or too few in number. The failure of Wellington’s first siege of Badajoz in 1811 is attributed in part to a chronic shortage of engineers. Mistakes by, or the absence of, engineers could cause significant friendly casualties. Thus, the importance of cities to warfare was recognized in the effort and cost undertaken by armies to develop and train specialized troops to meet the particular requirements for successful operations against cities.