Spontaneous and stimulated radiations of a classical moving charge from energy conservation

In classical electrodynamics the amplitude of the radiation by a charged particle in non-uniform motion is usually derived from the Liénard-Wiechert retarded potential. We show that it can be derived in a simpler way by supposing an initial radiation field which stimulates the emission and using energy conservation. We also compare the forces which brake (or accelerate) the particle in spontaneous and stimulated emissions (or absorption).