The 1808 invasion of Spain was, by his own admission, one of Napoleon Bonaparte's worst decisions and led eventually to his defeat at Waterloo. His rationale for invading Spain was to prevent Portugal from importing British products and to control access to the Mediterranean Sea. Napoleon's seasoned troops overwhelmed the Spanish defenses, but not the will of the people to resist. Though their army was defeated, their king deposed, and their country occupied, the Spanish would not give up. They had no hope of defeating the French in a pitched battle, so they used guerilla tactics, such as raids, ambushes, and sabotage, to harass the occupying army and disrupt its supply lines. To punish the guerillas and terrorize their sympathizers, the French raped, tortured, and killed civilians, and in return the Spanish guerillas perpetrated their own atrocities. It was a dirty, savage war. The longer it wore on, the more the civilian population suffered. When Spanish guerillas prevented supplies from entering Madrid, to weaken Bonaparte's puppet king, there was a severe shortage of food. Sick of the carnage and starvation, the former court painter Francisco Goya y Lucientes (1746-1828) made a series of etchings to document the devastation of his country and reveal what he evidently felt to be the innate brutality of humankind.
Cole TB. Los Desastres de la Guerra. JAMA. 2011;306(5):466. doi:10.1001/jama.2011.1033