Inventions, ideally, are result of needs and necessities of a certain generation of humankind. Human beings prospered and progressed over time because of his inquisitive nature and the ability to explore. Discoveries and inventions helped them to know more about the mother earth and made them to make their stay on this planet more comfortable. Needs and necessities of different ages and times encouraged humankind to come up with new inventions, however, some inventions simply originated to serve the whims and fancies of some men in authority who abused their influence and knowledge to invent something which put a questionmark on mere existence of human race on this planet. An invention without which this world would be a much better place is the invention of weapons of mass destruction also known WMDs.
A weapon of mass destruction is a nuclear, radiological, biological, chemical or other weapon that can kill and bring significant harm to a large number of humans or cause great damage to man-made structures (e.g. buildings), natural structures (e.g. mountains), or the biosphere. These weapons were developed initially by industrialized nations liks United States, Japan, Germany etc as a weapon of self defence to deter the enemy against any possible aggression and attack (Deterrence theory of international politics). However, in due course of time these weapons emerged as a threat to the very existence of human race on this planet. The deterrence theory failed to prevent wars and battles between nations and rather led to beginning of an arms race between nations. India and Pakistan, 2 south asian neighbours developed nuclear weapons in 1998 but still had a war in 1999 and still have skirmishes on their borders on almost daily basis.
The application of nuclear bomb by United States against Japan, use of chemical weapons by Germans against Jews in concentration camps made the world to realize the ferocity and dangers of these
References: 1. http://www.brainyquote.com/quotes/keywords/weapons.html#w4hFA17ZzOdtj8bc.99 2. https://www.goodreads.com/quotes/tag/weapons-of-mass-destruction 3. http://en.wikipedia.org/wiki/Weapon_of_mass_destruction 4. http://sangwhopark.blogspot.in/2011/11/18-what-invention-would-world-be-better.html