Council of Elrond

CRF, Turn Sequence, Movement/Hazard Phase, Returning to Site of Origin wrote:An effect that returns a company to its site of origin may not be declared in the middle of an attack.

Long Winter wrote:Environment. Each moving company that has at least two Wildernesses [w] in its site path must return to its site of origin unless it contains a ranger. Additionally, if Doors of Night is in play, each non-Haven site card with at least two Wildernesses in its site path is tapped. Cannot be duplicated.

What will happen if a company that is facing an attack and that has two in its site path will lose a last ranger during combat?
Will the action "return to a site of origin" be choked off (as unable to being declared)?
Or will be it postponed to a next chain of effect that will happen after facing of the attack?
Or something else?

That rule lost me at declaring an effect.