Killing technology has been on show during the major wars in the 20th century; and the killing rate increased drastically in the last century. During 20th century major developments took place in gas weapons, small arms, large guns and weapons of mass destruction which were in use during World War 1 and World War 2. Killing was not seen as an objective in war however, it was seen as being a more humane method and to make war shorter. The First World War was described as “chemists’ war” due to the improvement in gas warfare; the Second World War described as “physicists’ war” due to the development of weapons of mass destruction. Some technologies or practices that were developed for the purpose of killing during warfare have been introduced into capital punishment or personal protection. , 
During the Great War the poison gas was one of the most feared weapons even though it was machine guns that ultimately killed the largest number of people. These gases comprised of lethal elements like phosgene and chlorine; it was a major component in First World War and was very widespread which gave many people the view that it was “the chemists’ war”. One of the advantages of gas attack compared to the conventional artillery was that hiding in the trenches alone wasn’t an option anymore. Though there was no instant death with poisonous gases it would leave anyone in heavy contact with it in agony for days. In order to counter the poison gas effect many countries had come up with gas masks, it significantly reduced the number of casualties however, the soldiers who were not able to use the masks were often left in distress and they would eventually die. Poisonous gases was a terrifying weapon however its impact rather like the tank isn’t obvious, during the war it only caused 3% of the fatalities. The use of lethal gases would be further used in wars again for killing of civilians and also for capital punishment. , , 
There have been times over the last century where the government have innovated or developed new technology to eliminate a large number people from the population. There are examples in the Great War where the Ottoman Empire killed large numbers of (estimated 1.5 million) Armenians during their deportation from their central Anatolin territories. The Japanese killed 100-300,000 Chinese soldiers after their capture of Nanking. These genocides were mostly performed by shooting via conventional weapons such as small arms. 
One of the practices developed during the Second World War and perhaps the most well known by the Nazi is the use of gas chambers. These gas chambers were used within the extermination camp as part of Action T4 program which was aimed at eliminating German people who were deemed physically and mentally disabled ("judged incurably sick, by critical medical examination") and people who opposed the Nazi principles. During the Holocaust these gas chambers were modified to host large numbers of Jews as a part of Nazi policy of genocide. They used hydrogen cyanide based pesticide called Zyklon B to poison the people in the gas chambers of their extermination camps and it became a central symbol of the Holocaust. Zyklon B gas chambers were not the only method used by Nazi for mass execution; for the first large scale killing (nearly 1.3 million) of Jews, in areas of Poland and Soviet Union conventional small arms methods were used by small killing squads. Carbon monoxide was the first gas used to kill people; it was available from the engine exhaust and its main advantage was that the killers didn’t have the direct task of killing. This technology had already been put on use to kill thousands of handicapped Aryans by 1942. However, these technologies didn’t symbolise the Holocaust as did the Zykon B. The use of gas to mass killing is to remove the element of direct human involvement in the process and also to make it more...