Why do military rockets carry both fuel and oxidizer?

Military rockets and missiles carry both fuel and an oxidizer because they are designed to operate independently of the Earth's atmosphere, including in the vacuum of space. Unlike air-breathing engines, such as turbojets, which draw oxygen from the surrounding air to facilitate combustion, a rocket must carry all of its necessary propellants on board to generate thrust.1

In chemical-rocket propulsion, the engine derives energy through the combustion of these propellants at elevated pressures. The fuel and the oxygen-rich oxidizer are mixed within the combustion chamber, where they react to produce hot gases. These gases are then accelerated through a nozzle to create the high-velocity exhaust required to produce forward thrust, following Newton's third law of motion. Whether using liquid-propellant systems—where fuel and oxidizer are stored in separate tanks—or solid-propellant motors—where both components are mixed into a solid casing—carrying both substances ensures the rocket can function in any environment.123