The Battle of Tsushima (Russian: Цусимское сражение, Tsusimskoye srazheniye), also known as the Battle of Tsushima Strait and the Naval Battle of the Sea of Japan (Japanese: 日本海海戦, Nihonkai-Kaisen) in Japan, was a major naval battle fought between Russia and Japan during the Russo-Japanese War. It was naval history’s first decisive sea battle fought by modern steel battleship fleets, and the first naval battle in which wireless telegraphy (radio) played a critically important role. It has been characterized as the “dying echo of the old era – for the last time in the history of naval warfare, ships of the line of a beaten fleet surrendered on the high seas”.

https://en.m.wikipedia.org/wiki/Battle_of_Tsushima

The Treaty of Portsmouth formally ended the 1904–05 Russo-Japanese War. It was signed on September 5, 1905 after negotiations lasting from August 6 to August 30, at the Portsmouth Naval Shipyard in Kittery, Maine, United States. U.S. President Theodore Roosevelt was instrumental in the negotiations and won the Nobel Peace Prize for his efforts.

https://en.m.wikipedia.org/wiki/Treaty_of_Portsmouth

Babi Yar (Ukrainian: Бабин Яр, Babyn Yar; Russian: Бабий Яр, Babiy Yar) is a ravine in the Ukrainian capital Kyiv and a site of massacres carried out by German forces during their campaign against the Soviet Union in World War II. The first, and best documented, of the massacres took place on 29–30 September 1941, killing approximately 33,771 Jews. The decision to kill all the Jews in Kyiv was made by the military governor Generalmajor Kurt Eberhard, the Police Commander for Army Group South, SS-Obergruppenführer Friedrich Jeckeln, and the Einsatzgruppe C Commander Otto Rasch. Sonderkommando 4a soldiers, along with the aid of the SD and SS Police Battalions with the Ukrainian Auxiliary Police backed by the Wehrmacht carried out the orders. The massacre was the largest mass killing under the auspices of the Nazi regime and its collaborators during its campaign against the Soviet Union and has been called “the largest single massacre in the history of the Holocaust” to that particular date, and surpassed overall only by the later 1941 Odessa massacre of more than 50,000 Jews in October 1941 (committed by German and Romanian troops) and by Aktion Erntefest of November 1943 in occupied Poland with 42,000–43,000 victims.

Victims of other massacres at the site included Soviet prisoners of war, communists, Ukrainian nationalists and Roma. It is estimated that between 100,000 and 150,000 people were killed at Babi Yar during the German occupation.

https://en.m.wikipedia.org/wiki/Babi_Yar