A two-stroke diesel engine is an internal combustion engine that uses compression ignition, with a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899. In compression ignition, air is first compressed and heated; fuel is then injected into the cylinder, causing it to self-ignite. The two-stroke cycle ignites the fuel to deliver a power stroke each time the piston rises and falls in the cylinder, without any need for the additional exhaust and induction strokes of the four-stroke cycle.