Historical Events in April 1815

Apr 5 Mount Tambora in the Dutch East Indies, has its first violent eruption after several centuries of dormancy

Apr 6 British militia shoots prisoners, 100's killed
Apr 10 Austria declares war on Kingdom of Naples
Apr 10 Mount Tambora in the Dutch East Indies experiences a cataclysmic eruption, one of the most powerful in history, killing around 71,000 people, causes global volcanic winter