After World War I, international law was established that banned biological and chemical weapons and attempted to shield civilians from the horrors of total war. Many believed that the intentional targeting of civilian populations would end. The Spanish Civil War of 1936 to 1939 shattered these illusions. Much like the experience of the 1930s, the invasion of Ukraine is shattering the illusion that aggression is a relic of the past, and a reminder that warmongering must be deterred by forceful resistance.