The First World War was the first truly global conflict, and warfare itself underwent many fundamental changes. Steel warships weighing thousands of tons exchanged fire while still miles apart. Below the waters, submarines were taking their toll on surface ships and thus proving their military value. On land, artillery and machine guns served to maintain the intractability of trench warfare, while newer inventions such as tanks and airplanes worked towards ending it.

After the Armistice, innovation continued in the civilian sector. Radio joined print as an important means of disseminating information. Penicillin and other antibiotics were discovered to treat a variety of infections. And women's suffrage planted the seeds of many civil liberties to come. It wasn't long, however, before the clouds of war were gathering again.

At the outbreak of the Second World War, many of the breakthrough weapons of the previous war had become indispensable. Rapid advances in the design and manufacture of combustion engines resulted in vastly superior tanks and aircraft. Additionally, the creation of entirely new propulsion systems eventually led to the first jets and long range rockets. Bazookas and anti-aircraft guns were developed as counter-weapons to tanks and aircraft, and anti-submarine warfare reached a new level with the deployment of sophisticated destroyers.

Humanity's overall appetite for science and technology — not to mention natural resources — intensified during and just after the war years. Mining techniques and machinery were improved. Television redefined life at home. Researchers developed vaccines for polio and other diseases and national vaccination policies were adopted. Even the structure of DNA, which contains the genetic code for life on earth, was discovered during this productive period. But the defining event of the Atomic Age was the splitting of the atom and subsequent development of both atomic weapons and controlled-fission reactors. It was to have lingering consequences.

In the latter half of the Century, the Cold War dominated the international policies of many countries and nuclear weapons played a crucial role in deterrence. These "weapons of mass destruction" were so devastating that a single warhead could wipe out a city, and implicit threats worked to maintain an uneasy peace. To transport the warheads to their targets, nuclear nations developed heavy long-range bombers, Intercontinental Ballistic Missiles (ICBMs), and strategic submarines. Also important was the invention of the microcomputer, which opened the door to these and other high-tech weapons systems such as the M1 tank, the F-15 fighter, and the Apache helicopter. Surface-to-air missiles also came into wide spread use to help minimize threats from above.

But computers as well as advances in communications were not limited to military uses. They had everyday applications in business and industry, and also in private life. And, like the atom, they would soon define an Epoch of human development.