This Day in History: September 17

642 Arab forces led by Amr ibn al-'As seizing control over Alexandria

The Arab forces, under the command of Amr ibn al-'As, successfully conquered Alexandria, marking a pivotal point in the history of Arab conquests.

1683 Discovery of bacteria by Antonie van Leeuwenhoek

Dutch scientist Antonie van Leeuwenhoek became the first to report the existence of bacteria, revolutionizing the field of microbiology.

1787 Signature of the US Constitution by delegates at the Philadelphia Convention

The US Constitution was endorsed at the Philadelphia convention by the delegates. This development marked the advent of a new governance system for the United States.

1862 The Battle of Antietam, the bloodiest day in the American Civil War

Known as the Battle of Sharpsburg, this was the deadliest day of the American Civil War. The first battle on Union soil witnessed 22,000 casualties- dead, wounded, or missing.

1916 The Red Baron's first aerial combat victory

World War I flying ace known as the Red Baron of the German Luftstreitkräfte, claimed his first triumph in an aerial combat near Cambrai, France.

1940 Hitler postpones Operation Sealion indefinitely

Adolf Hitler called off Operation Sealion, the planned German invasion of Great Britain, indefinitely, shifting the course of World War II.

1978 Signing of the Camp David Accords

Anwar Sadat, Menachem Begin, and Jimmy Carter signed the Camp David Accords, setting the groundwork for peace in the Middle East and between Egypt and Israel. This initial accord led to the 1974 Egypt-Israel Peace Treaty.

1939 Record-setting 10,000-meter run in less than 30 minutes

Finnish runner Taisto Mäki made history by completing a 10,000-meter run in under 30 minutes for the first time on record, breaking his own previous best time.

1894 Japan's victory at the Battle of the Yalu River

A day after winning the Battle of Pyongyang, Japan defeated China in the Battle of the Yalu River, also known as the Battle of the Yellow Sea. This conflict was a significant part of the First Sino-Japanese War.

1809 Sweden and Russia sign the Treaty of Fredrikshamn

The Treaty of Fredrikshamn, also known as the Treaty of Hamina, marked the end of the Finnish War. The treaty resulted in the cession of Swedish territories, which later became Finland, to Russia.