He needs to add that the deportation may not be to their country of origin.
Honestly an effort of that large scale can't possibly sort everyone out, 5 million from mexico, 5 million back,1 million from Gaza, 1 million back. . . . Since they are undocumented, we have no way of knowing where they came from. Gaza to Mexico, Ukraine to Gaza, Mexico to Ukraine, it really doesn't matter to us who goes where. Those that are here to vote illegally might think twice if they come to the realization that the worst case is not that they will return to where they come from.
Build a southern railroad from Florida to a shipping port in South California. Collect all illegals and give them a ride on a container ship back to the shithole countries they came from. Take all Combatants send them to that famous one square mile, the pirates stronghold!