Army Abruptly Removes V Corps Commander from Poland-Based NATO Eastern Flank Post

The Army relieved Lt. Gen. Charles Costanza from command of V Corps — the forward-deployed headquarters in Poland responsible for NATO eastern-flank operations and coordinating US support to Ukraine — on August 7, 2026, roughly two months before his planned departure. An Army spokesperson said only that 'the matter has been referred to the appropriate authority in accordance with Army regulations,' without disclosing a reason. Brig. Gen. John Mountford, V Corps' deputy commander, is serving as acting commander; Maj. Gen. Thomas Feltey, already Senate-confirmed as Costanza's successor, had been due to take over in October. The removal lands amid a broader shake-up of senior military ranks under Defense Secretary Pete Hegseth, though a source familiar with the matter said Costanza's case is unrelated to that campaign.