Editing Siege (section)

===Emerging theories===
The castles that in earlier years had been formidable obstacles were easily breached by the new weapons. For example, in Spain, the newly equipped army of [[Ferdinand and Isabella]] was able to conquer [[Moors|Moorish]] strongholds in [[Granada]] in 1482–1492 that had held out for centuries before the invention of cannons.

In the early 15th century, Italian architect [[Leon Battista Alberti]] wrote a treatise entitled ''De Re aedificatoria'', which theorized methods of building fortifications capable of withstanding the new guns. He proposed that walls be "built in uneven lines, like the teeth of a saw". He proposed star-shaped fortresses with low, thick walls.

However, few rulers paid any attention to his theories. A few towns in Italy began building in the new style late in the 1480s, but it was only with the French invasion of the Italian peninsula in 1494–1495 that the new fortifications were built on a large scale. [[Charles VIII of France|Charles VIII]] invaded Italy with an army of 18,000 men and a horse-drawn [[siege-train]]. As a result, he could defeat virtually any city or state, no matter how well defended. In a panic, military strategy was completely rethought throughout the Italian states of the time, with a strong emphasis on the new fortifications that could withstand a modern siege.