Does "depleting the ranks of" mean "exhausting various level of"?

Context:
Western intelligence officials now believe that there are fewer than 300 sur-viving members of Al Qaeda, based mainly in Pakistan and Afghanistan, down from a peak of 3,000 to 4,000 fighters in the late 1990s. Most of Al Qaeda’s skilled operatives and mid-level field lieutenants have been either killed or captured, depleting the ranks of seasoned fighters and effective managers, and depriving it of significant operational capability. The bulk of Al Qaeda’s membership is now composed of cooks, drivers, bodyguards, and foot soldiers.
So profound is Al Qaeda’s disarray that one of its field lieutenants, in a mes-sage intercepted by U.S. intelligence, had pleaded with bin Laden to come to the group’s rescue and provide some leadership. His plea fell on deaf ears.