Jamieson, Fausset and Brown on Ezekiel 29:5

5. wilderness--captivity beyond thy kingdom. The expression is used perhaps to imply retribution in kind. As Egypt pursued after Israel, saying, "The wilderness hath shut them in" (Ex 14:3), so she herself shall be brought into a wilderness state.

open fields--literally, "face of the field."

not be brought together--As the crocodile is not, when caught, restored to the river, so no remnant of thy routed army shall be brought together, and rallied, after its defeat in the wilderness. Pharaoh led an army against Cyrene in Africa, in support of Aricranes, who had been stripped of his kingdom by the Cyrenians. The army perished and Egypt rebelled against him [Junius]. But the reference is mainly to the defeat by Nebuchadnezzar.

beasts ... fowls--hostile and savage men.