Recently, for the first time, the U.S. military released the test video of the f-35a fighter launching the new b61-12 nuclear bomb. The video shows the whole process of the f-35a fighter opening the bomb chamber to launch a simulated nuclear bomb, igniting the bomb in the air and autonomous navigation to hit the target. According to the information released by the US side, the test was completed at tonopa proving ground, Nevada, on August 25 this year. According to media reports, the test represents an important step in the actual combat of US nuclear weapons. Since its birth, nuclear weapons have been mainly used for deterrence due to their destructive effects. However, in recent years, the U.S. government has repeatedly claimed that its existing nuclear deterrence strategy is outdated. The growing nuclear power of other major powers and the development and use of “asymmetric” means pose a real threat to the United States. To this end, the United States needs to formulate diversified response plans including nuclear strike. During Trump’s administration, in order to maintain the military advantage of the United States, the United States government paid more and more attention to the theory of “actual combat of nuclear weapons”, but the “excessive killing” of nuclear weapons has always been the bottleneck restricting the practical use of such weapons. In order to break through this bottleneck, the US military began to turn its attention to new low yield tactical nuclear weapons. < / P > < p > low yield tactical nuclear weapons are small in size, light in weight, good in mobility, and low in yield. They can be projected by means of artillery, short-range surface to surface missiles, tactical aircraft, and torpedoes. Their main purpose is to strike important targets in the depth of enemy’s campaign tactics and help their own side gain battlefield advantage. During the cold war, both the United States and the Soviet Union produced and equipped a large number of tactical nuclear weapons, but due to the problems of low hit accuracy and nuclear pollution, tactical nuclear weapons were never put into actual combat. < / P > < p > with the development of precision guidance technology, tactical nuclear weapons are once again full of vitality. The U.S. military believes that by developing and deploying small nuclear weapons and cooperating with high-precision projective vehicles, it can not only directly support land, sea and air battlefield operations, make up for the lack of conventional strike capability, strike important targets in the enemy’s tactical depth, but also form a full spectrum deterrent with different power and damage effects. To this end, the U.S. defense budget bill for fiscal year 2020 will increase the cost of developing low yield nuclear bombs by 8.3%. < p > < p > in the new round of US military low yield tactical nuclear weapon research and development, B61 nuclear bomb is one of the key points. The B61 nuclear bomb has served in the US military for more than 60 years. The b61-12 in this test is the latest model of the B61 nuclear warhead life extension program, weighing 700 kg and 4 meters long. The key points of improvement are to add spinning rockets, safety and safety devices, install new precision guidance tail components and new guidance system, and the circular probability error is said to be no more than 30 meters. Its warhead has four kinds of optional explosive equivalent, and has the ability to drill into the ground. Earlier this year, the b61-12 nuclear bomb was tested on the F-15E fighter, making it the first fighter compatible with the b61-12 nuclear bomb. < / P > < p > some analysis points out that this test is of great significance to the actual combat of U.S. nuclear weapons. At present, B-2 and b-52h strategic bombers are the main force of us air based nuclear strike. The US air force believes that it is difficult for b-52h strategic bombers, which have been equipped with troops since 1961, to effectively break through the modern air defense network of potential competitors. At the same time, B-2 stealth bombers in service and b-21 bombers in service can only fly at subsonic speed due to aerodynamic layout and other reasons. In addition, the F-15E fighter, as an air-based tactical nuclear weapon delivery platform, has an average service life of nearly 30 years, and its stability and reliability are worrying. < / P > < p > in this test, the f-35a fighter launched the b61-12 simulated nuclear bomb at an altitude of 3200 meters, and hit the target 42 seconds after the launch. This test is the first time that the US military has conducted a comprehensive test on the future tactical nuclear strike system, and it is also the first time that the b61-12 nuclear bomb has been launched from an internal magazine. < / P > < p > according to the US military plan, some f-35a fighters will be converted into both nuclear and conventional fighters in the fourth batch of upgrading, each of which can carry a b61-12 nuclear bomb. As a fifth generation fighter with supersonic stealth performance, the combat capability and penetration capability of f-35a fighter to advanced air defense system are worth mentioning. If the f-35a fighter is combined with the new tactical nuclear weapons, it will greatly enhance the feasibility of the US military’s tactical nuclear strike, and then lead to the lowering of the nuclear threshold. It is not only possible to trigger a nuclear race among the nuclear weapon states, which will lead to the retrogression of nuclear disarmament achievements, but also increase the risk of nuclear conflict.