Blocker Gundan 4 Machine Blaster was an anime series aired from 1976 to 1977 in Japan. There were 38 episodes aired at 25 minutes each. It is also known as "Blocker Army IV Machine Blaster", "Blocker Corps IV", "Blocker Army IV", "Blocker Corps", "Machine Blaster".
Earth is being attacked by the Moguru civilization, a super advanced peoples that live beneath the ocean. Professor Yuri, having studied the ancient super-technology in Astro base, anticipated such an invasion would take place. Using what he had learned of rheir technology, he created a series of super robots to help repel any such invasion, known as the Machine Blaster Corps. Led by the pilot Ishida, the Blocker Corps stands firm against the attack of the Moguru rulers, Hellqueen V and Kaibuddha.
The number 4 comes from the team of 4 robots. The robots individually have their own weapon, but they can also be combined to form a fire ring which cuts through the enemies. It was not the most popular show since anime powerhouses Gaiking and Combattler V, which featured more creative combinations and designs, were ruling the airwaves.