Investigators have found the inability of senior Marine Corps commanders to keep up with the demands of the pandemic, rising tensions with Iran, and the militarization of the U.S.-Mexico border may have contributed to the accidental deaths of nine Marines last year. In a new report released on Wednesday, Lt. Gen. Carl Mundy III said it would be “a mistake to discount or overlook” these factors as having contributed to the sinking of an amphibious assault vehicle off the Southern California coast in July 2020. It does not excuse the top officials previously faulted for the accident, which was found to be “preventable,” including Maj. Gen. Robert Castellvi, who was dismissed from his post as the commanding general of 1st Marine Division at Camp Pendleton following the incident.

Other aggravating factors stretching the Marines’ time and resources were defense assignments at the southern U.S. border, and “planning for major combat operations due to heightened tensions with Iran in January 2020,” according to the report. Investigators also found that the victims’ deployment, 15th Marine Expeditionary Unit, had not completed training required to operate the amphibious assault vehicles they were provided, including on how to escape a sinking machine. “This tragedy should never have occurred,” a senior commander, Vice Adm. Roy Kitchener, said. “We will not let the lives be lost in vain.”