On 20 March 1811, Marie Louise gave birth to a baby boy, whom Napoleon made heir apparent and bestowed the title of King of Rome. His son never actually ruled the empire, but given his brief titular rule and cousin Louis-Napoléon's subsequent naming himself Napoléon III, historians often refer to him as Napoleon II.
It began on 20 March 1848 and resulted in Prussia annexing the Greater Polish region as the Province of Posen.
In March 1920, Tomás Mac Curtain, the Sinn Féin Lord Mayor of Cork, was shot dead in front of his wife at his home, by men with blackened faces who were seen returning to the local police barracks. The jury at the inquest into his death returned a verdict of wilful murder against David Lloyd George (the British Prime Minister) and District Inspector Swanzy, among others. Swanzy was later tracked down and killed in Lisburn, County Antrim. This pattern of killings and reprisals escalated in the second half of 1920 and in 1921.
The controversial Economy Act of 1933 is signed into law, slashing $243 million in government salaries and pensions, and veterans' benefits. Despite the economic crisis, super majorities of American economists, policymakers, and the general public believed that the federal government needed to balance the budget and avoid deficit spending, to avoid putting further strain on the bond market which would negatively affect government borrowing costs, banks, corporations, and foreign investors. From 1929 to 1933, the total debt owed by the U.S. government rose from $16.9 billion to over $23 billion.
On 20 March 1943, Mao Zedong became the Chairman of the Communist Party of China, and to enhance the Red Army's military operations, Mao as the Chairman of the Communist Party of China, named his close associate General Zhu De to be its Commander-in-Chief.
On 20 March, Thieu reversed himself and ordered Huế, Vietnam's third-largest city, be held at all costs, and then changed his policy several times. As the North Vietnamese launched their attack, panic set in, and ARVN resistance withered.
On 20 March an aid convoy with medical supplies and doctors reached Maglaj, a city of 100,000 people, which had been under siege since May 1993 and had been surviving off food supplies dropped by US aircraft. A second convoy on 23 March was hijacked and looted.
On March 20, 2008, the IPO underwriters (including JP Morgan, Goldman Sachs & Co., Bank of America Securities LLC, Citi, HSBC, Merrill Lynch & Co., UBS Investment Bank and Wachovia Securities) exercised their overallotment option, purchasing an additional 40.6 million shares, bringing Visa's total IPO share count to 446.6 million, and bringing the total proceeds to US$19.1 billion.
On 20 March, Erdoğan made a speech promising to "rip out the roots" of the Twitter service. Hours later the telecommunications regulator BTK blocked DNS service to the site, citing four court orders the Turkish government had made requiring them to remove content to preserve privacy that had not been heeded. Sources covering the story attributed this to the use of Twitter to share links to the Erdoğan recordings on YouTube. Erdoğan also threatened to ban Facebook.
On March 20, 2014, Facebook announced a new open-source programming language called Hack. Before public release, a large portion of Facebook was already running and "battle tested" using the new language.
Apple announced the 2nd generation AirPods on March 20, 2019. They are the same design as the first generation but have updated features. They include an H1 processor which supports hands-free "Hey Siri", Bluetooth 5 connectivity. Apple also claims 50% more talk time and faster device connection times. The "Announce Messages with Siri” feature was added in iOS 13.2, which allows the user to dictate text messages to Siri.
In March 2018, Feige revealed that the majority of characters would be back with Marvel Studios, though there were still "some with a couple of other players involved that would have to be negotiated with." The deal was completed on March 20, 2019.
On March 20, 2019, at the Game Developers Conference, Facebook announced the Oculus Rift S, a successor to the original Oculus Rift headset. It was co-developed with and manufactured by Lenovo and launched at a price of US$399. The Rift S contains hardware features from the Oculus Go and Oculus Quest, including Oculus Insight, integrated speakers, and a new "halo" strap. The Rift S uses the same 1440p fast-switching LCD display and lenses as the Oculus Go (a higher resolution in comparison to the original model, but lower in comparison to Oculus Quest), running at 80 Hz, and is backward compatible with all existing Oculus Rift games and software. Unlike the original Oculus Rift, it does not have hardware control for inter-pupillary distance.
On March 20, 2019, the European Commission imposed a €1.49 billion ($1.69 billion) fine on Google for preventing rivals from being able to “compete and innovate fairly” in the online advertising market.
On 20 March, the government announced that all leisure establishments (pubs, gyms, etc.) were to close as soon as possible, and promised to pay up to 80% of workers' wages, to a limit of £2,500 per month, to prevent unemployment in the crisis.
By 20 March, the four incursion fronts had formed a perimeter significantly within the entire border of Eastern Ukraine and started to extensively consolidate lines of communication and support between all four fronts within Ukraine while besieging Mariupol, Kiev, Donbas, Luhansk, and other cities.