The people who are closing the doors - because they are *full* - are not going to
care about niceties as "back to where?". Those are the luxuries expressed by the
vocal (but unhelpful) armchair "activists" from thousands of miles away.

The thing about triggering a "door shutting event" is that it cascades to the next
nation, the one who can no longer stand aside in order to let people pass through
to "somewhere else". That, in turn, triggers the door to be shut in each poor,
increasingly nationalistic nation: the doors that were only remaining open as long
as the exit doors were equally open. Once the exit door closes, the danger from
the combination of frustrated migrants and frustrated nationalists hits ignition
temperature very quickly. All that government can hope to do - in order to maintain
any form of public order - is close the "IN" door.

This will inevitably lead to two things: the first is that the accumulation of migrants
causes border issues; the second is that the strain on the country's structure exceeds
the ability to meet demands. The first issue allows the nationalists to have a free
target of "others" to blame for problems - law breakers from "out there".
The second issue gives the support for the growth of the nationalist response - the
increasing number of innocent citizens who are being impacted by the migrants.

Those people simply will not care about the "where" to send them "back" to.

If there is not a voluntary "retreat" by the people perceived as an "invading army"
then the "where" will be a bloody mess to be talked about by future historians.
(cf. Balkans, Rwanda, etc.)

"Where" at this point resolves to "away", not to a useful destination.