The phrase "adjoining territories" is correct and usable in written English.
It is typically used to refer to two or more territories belonging to the same nation which share a common border. For example: "The government issued a statement that the two adjoining territories should work together to develop an effective cross-border strategy."
Serbia has suffered very deeply, as have the adjoining territories.
Map of the territory of Montana with portions of the adjoining territories / compiled and drawn by W.W. De Lacy, civil engineer & surveyor, Helena, M.T. 2nd ed., corr.
Map of the territory of Montana with portions of the adjoining territories / compiled and drawn by W.W. De Lacy of the Surveyor General's Office.
Map of the Territory of Montana with portions of the adjoining territories / drawn by W.W. de Lacy for the use of the First Legislature of Montana.
Bordeaux, for example, recognizes that adjoining territories can have differing characteristics and so distinguishes Pauillac from St-Estèphe, and St-Julien.
Nevertheless, David was so angered by the oppressive administration of English officials in adjoining territories that on March 22, 1282, he attacked the English garrison at Hawarden, Clwyd, thereby precipitating the final struggle for national independence.
Map of the Catskill Forest and adjoining territory, compiled from maps and field notes, partially revised 1911 by E.B. Codwise.
Last October, militiamen arrived with workmen and cleared some of her land and adjoining territory to build storage units.
Map of the Adirondack Forest and adjoining territory : compiled from the official maps and field notes on file in the State Department at Albany, N.Y.
Rwanda and Uganda, which like Angola had originally helped Mr Kabila to power in the hope that he would squash their rebel movements in adjoining territory, are so disappointed with his failure to do so that they now support the Congolese rebels fighting him.
The Toledo War (1835 36), also known as the Michigan Ohio War, was the almost bloodless boundary dispute between the U.S. state of Ohio and the adjoining territory of Michigan.
