What new weapons and tactics emerged from World War II?

Necessity, it is said, is the mother of invention, and the developments of warfare that took place during World War Two bear this out. While the twentieth century witnessed a boom in advances in military technology, by the end of World War Two, the war in the air, in particular, had been entirely transformed from the early days of World War One, when soldiers shot at each other using unanchored guns from propeller-driven biplanes.
The invention of the jet engine, certainly, was one of the advances that changed the course of the war and flying in general. The jet engine was actually invented and patented in 1930 by Frank Whittle, but it was the Second World War which spurred Whittle into action; a flight test was performed in 1941. This technology was shared with the Americans by the Royal Air Force, meaning that the two nations were able to independently develop faster and more powerful airplanes. At the same time, German engineers were independently developing similar advances in jet engine technology. The result was that airplanes were able to cover longer distances, fly faster, and stay airborne for longer. Massive battles in the air, such as the Battle of Britain, and long flights, such as the US expedition to Hiroshima, would not have been possible without the growth of aeronautical technology.
This leads us on to the second key advancement in military technology resulting from World War Two: the atom bomb. Again, Allied scientists were not the only ones who were making advances in this arena—indeed, scientists were propelled by fears that German scientists had already developed a nuclear weapon. Albert Einstein, a refugee in the United States, convinced President Roosevelt to embark on research in this area, and by 1945, a weapon was ready to be tested. The first bomb was tested in New Mexico, and the dropping of the atom bomb on Hiroshima, Japan, is generally thought to have hastened the end of the war. This massive shift in weapons technology led the world into a new age of fear and stalemate, which would become known as the Cold War: weapons and scientific developments were pitted against each other, but strikes were more generally feared rather than enacted.