On April 11, 1861, Confederate forces under General P.G.T. Beauregard delivered an ultimatum to Union Major Robert Anderson, commander of the besieged Fort Sumter, demanding immediate evacuation. Anderson refused, citing orders and dwindling supplies. Hours of tense negotiation followed before Beauregard's guns opened fire at 4:30 the next morning, igniting the American Civil War.

As US forces approached, Buchenwald's underground resistance organization overpowered the remaining guards and raised a white flag. Soldiers of the 6th Armored Division, Third Army, entered the camp on April 11, 1945, discovering scenes of mass starvation and death that shocked even hardened combat veterans and provided searing evidence of Nazi atrocities.

On April 11, 1961, Adolf Eichmann's trial opened in a Jerusalem courtroom, nearly a year after Israeli Mossad agents captured him in Argentina. Charged with crimes against humanity for his role organizing the logistics of the Holocaust, Eichmann sat behind bulletproof glass. The proceedings, filmed and broadcast internationally, forced a global reckoning with the mechanics of genocide.

Apollo 13 launched at 13:13 local time, carrying Jim Lovell, Jack Swigert, and Fred Haise toward a planned lunar landing. Two days later, an oxygen tank ruptured, forcing NASA and the crew into a desperate improvised rescue that became one of spaceflight's most celebrated survival stories.

On April 11, 1976, Steve Jobs, Steve Wozniak, and Ronald Wayne signed a partnership agreement founding Apple Computer Company. Wozniak had already built a working prototype, the Apple I, and the trio aimed to sell fully assembled circuit boards to hobbyists through the Homebrew Computer Club scene. Wayne sold his 10 percent stake back for $800 just twelve days later, missing out on what would become one of history's most valuable companies.