Ignoring, for the moment, travelling wave antenna, and restricting
discussion to standing wave antennae ...

A wave is launched, and radiates SOME of the power, and suffers
both I2R losses and dielectric and permeability losses associated
with creating and collapsing the near field.

At first, there is no standing wave, until the wave reaches the point of
reflection
in the antenna and heads back the way it has come (because not all has been
radiated*****)
On the way back, it againn suffers the losses described above, as well as
radiating a
bit more.

It then reaches the other end and suffers further reflections ad infinitum.

An interesting conclusion is, therefore, that the I2R losses are repeated,
each tiome with a smaller loss, as the wave decrements.

***** Without the remnants of non-radiated power, there could NOT be
a standing wave!