Throughout the course of their history the humans had many wars and crusades motivated by hunger, disease and religion. Humans have been divided into many Empires and civilizations like the Hittites, Sumerians, ancient Egyptians and the Roman Empire. By the 17th Century, Humans had divided into many permanent civilizations like the modern day Nations of China, Britain (which at the time was known as the British Empire) from which occupied nations began to be granted independence like the United States, Australia, India and so on. By the early 20th Century the Human race had split into two main alliances, the Central Powers and the Triple Entente from which both powers fought for supremacy and dominance of Earth in a conflict known as World War 1 (1914–1918), which ended in the Central Powers' defeat and the disbanding of the Triple Entente, and the creation of the League of Nations.
World War 2 (1939–1945) followed with the League of Nations or the United Nations fighting the Third Reich (or Nazi Germany) and the Empire of Japan, the conflict lasted for six years but eventually led to the Axis Powers surrendering and the birth of many organizations such as the UN (United Nations), the EU (European Union), and NATO (North Atlantic Treaty Organization).
The Cold War (1947-1991) had started after WWII, with competition between Capitalism and Communism. Tensions between the United States (aided by NATO) and the Soviet Union (leading the Warsaw Pact) began. Although, there wasn't any direct military conflict, they fought proxy wars in Korea, Vietnam, Afghanistan and so on. The Berlin Wall kept Germany divided. There was West Germany, which was under NATO, and East Germany, which was under the Warsaw Pact. Fears of "nuclear war" raised in both sides. The Cold War ended after the Soviet Union collapsed, creating 15 new countries, and when the Berlin Wall was taken down, with West and East Germany united again for the first time since 1945.
The Human race is now a spacefaring race as Earth's resources were eventually depleted, due to a Third World War and mankind united in the form of the UCN and the ISA. The humans have had one war in the Alpha Centauri System and another which is in progress, they are currently fighting the Helghast Empire, an organization with similarities to infamous historical regimes of Earth.
Human Technology is very advanced by the 24th Century in some fields, but they still use ballistic weaponry, the vehicles use locomotive engines and their air and spacecraft use rotorcraft and rocket technology, respectively. Human technology includes Warp drives, micro missiles, attack drones that use anti-gravity, and body armor that can provide protection from the Vacuum and radioactive particles in space.