Nuclear war, or atomic war, is war in which nuclear weapons are used in a wide attack aimed at an entire country, both military and civilian targets. The United States is the only nation to have actually used nuclear weapons in war, having in 1945 dropped two of them on cities in Japan — one on Hiroshima and another on Nagasaki. That time the possibility of an actual nuclear attack on the US was considered somewhat remote because no other nation had nuclear weapons. But on August 29,1949 the USSR tested its first bomb at Semipalatinsk in Kazakhstan. Britain tested its first atomic bomb in 1952, and France in 1960. Notably the Western European arsenals have always been nearly insignificant compared to those of the superpowers — Russia and the United States. So, in the end of the Second World War the nuclear weapons race between two superpowers started. The nuclear war between these two superpowers was more likely till the end of the 20 the century» when the Soviet Union collapsed. With the end of the Cold War and the collapse of the Soviet Union nuclear conflict between the United States and Russia appears much less likely. Stockpiles of nuclear warheads are being reduced on both sides and tensions between the two countries have greatly reduced. Today current fears of nuclear war are mainly centred around India, first nuclear bomb test and Pakistan, first nuclear bomb test May 1998, because of their territorial dispute in Kashmir and mutual possession of substantial, though probably numbered in dozens rather than thousands. Therefore their nuclear arsenals make many extremely nervous. Moreover both have waged several wars over the conflict in Kashmir. Nuclear terrorism by non-state organisations could well be more likely, as states possessing nuclear weapons are susceptible to retaliation in kind. Geographically-dispersed and mobile terrorist organizations are not so easy to discourage by the threat of retaliation. Furthermore, while the collapse of the Soviet Union ended the Cold War, it greatly increased the risk that former Soviet nuclear weapons might become available on the black market. Using such a weapon as a foundation, a terrorist might even create a salted bomb capable of dispersing radioactive contamination over a large area, killing a greater number of people than the explosion itself. According to the recent scientific estimates any large-scale military conflict with the use of nuclear weapons can result in nuclear winter or summer and global climate change killing the majority of living beings. Nuclear winter is a hypothetical global climate condition that was predicted to be a possible outcome of a large-scale nuclear war. It is thought that severely cold weather would be caused by detonating large numbers of nuclear weapons, especially over flammable targets such as cities, where large amounts of smoke and soot would be injected into the Earth's stratosphere. This layer of particles would significantly reduce the amount of sunlight that reached the surface. Smoke and soot arising from the burning petroleum fuels and plastics would absorb sunlight very effectively. The ash would be carried by the midlatitude west-to-east winds, forming a uniform belt of particles encircling the northern hemisphere from 30° to 60° latitude. These thick black clouds could block out much of the sun's light for a period as long as several weeks, causing surface temperatures to drop by as much as 20C. The combination of darkness and killing frosts, combined with high doses of radiation from nuclear fallout, would severely damage plant life in the region. The extreme cold, high radiation levels, and the widespread destruction of industrial, medical, and transportation infrastructures along with food supplies would trigger a massive death toll from starvation, exposure, and diseases. It is also thought that nitrogen oxides generated by the blasts would degrade the ozone layer. Secondary effects from ozone depletion and concomitant increases in ultraviolet radiation would be significant, with impacts on the viability of most human staple agricultural crops as well as disruption of ocean food chains by killing off phytoplankton. After that a so-called nuclear summer can happen which would worsen the situation. A Nuclear summer is a hypothetical scenario resulting from a nuclear war that would follow a nuclear winter. In this scenario, after the nuclear winter the amount of water in the stratosphere would" increase, causing greenhouse warming of the surface. It would happen because thick clouds of soot and smoke over burning cities would reflect the major amount of sunlight that would be generated in the stratosphere, accumulating water. Also the nuclear detonations would also produce a great amount of oxides of nitrogen that would then deplete the ozone layer around the Earth. It is a common knowledge that this layer screens out sun ultraviolet radiation, which causes genetic damage to life forms on the surface. The absorption of ozone also results in a heating of the stratosphere, which results in a further contribution to greenhouse heating.
