After repeated delays, India successfully test fired the 3,500 km range K-4 nuclear-capable missile meant for the indigenous Arihant-class submarines. The missile was tested Sunday from a fixed underwater pontoon on the east coast — sources told ThePrint it was fired off the coast of Andhra Pradesh.This is the fourth time the Defence Research and Development Organisation (DRDO) has attempted to test fire the missile since October, but various climatic conditions prevented it. The K-4 is the most potent missile in India’s inventory that can be fired from a submarine, giving the country unprecedented second-strike capability and a huge deterrence power.While India does operate a submarine launched ballistic missile (SLBM), the K-15, it has a limited range of just about 750 km. DRDO sources say that the research agency is already working on a much longer range missile, the K-5, which can hit targets 5,000 km away.Notably, India is among the six nations in the world to have the capability to fire a nuclear missile from land, air and undersea. The others are US, Russia, China, France and UK.