  The strong-field approximation for high-harmonic generation in near-infrared
and infrared laser pulses is formulated in the accelerated Kramers-Henneberger
frame. The accompanying physical picture is discussed and the nature of the
leading-order term is contrasted with that of the three-step model following
the strong-field-approximation formulation in the length or velocity gauges.
The theory is illustrated by high-harmonic generation spectra for atomic
hydrogen.
