WASHINGTON — President George W. Bush spoke with his military commander in Iraq nearly every week.

President Barack Obama was so deeply involved in military operations that his first three Defense secretaries all complained, sometimes bitterly, about what they considered White House micromanagement.

In nearly five months in office, President Donald Trump has yet to meet or speak with either his Iraq or Afghanistan commander, even as his administration weighs deeper and longer-term involvement in both conflicts and asks Congress for a vast increase in defense spending.

Trump’s hands-off approach to America’s longest wars demonstrates how much control his administration has entrusted to Defense Secretary Jim Mattis, a retired four-star Marine general, and commanders on the ground.

Senior Pentagon officials and military officers have welcomed the shift, saying it has freed them to carry out operations based on military, and not political, considerations.

But it also raises concerns that Trump has given too much latitude to the Pentagon, which already has been accused of more indiscriminate bombings than in the past, causing an increase in civilian casualties.

“The idea of the 10,000-mile screwdriver from Washington making decisions for a field commander, as has been the case over the past decade, is flawed,” said James Stavridis, a retired admiral who served as NATO supreme commander and is now dean of the Fletcher School of Law and Diplomacy at Tufts University.

“We need to be cautious that we do not go so far in the other direction that we end up with rogue commanders,” Stavridis added. “The White House needs to lay out a strategic vision but then let commanders do the tactical execution.”

The president already has granted Mattis authority to raise troop levels in the wars in Iraq and Syria, a power usually held closely by the White House.

Trump is expected to grant Mattis the same authority in Afghanistan. The president also has authorized his commanders to move more aggressively against militants in Somalia and Yemen.

“What I do is I authorize my military,” Trump said April 13 after the Air Force dropped the most powerful conventional bomb in its arsenal on an Islamic State complex in eastern Afghanistan, a decision that was made without White House input.

A White House official, who wasn’t authorized to speak on conversations in the chain of command, said the delegation of authority has enabled commanders to take a “more aggressive approach” in which missions are executed with “more speed and more efficiency.”

Trump has regular working dinners with his national security team, aides say, and thus remains briefed on major operations. His companions include Mattis, Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff; Lt. Gen. H.R. McMaster, Trump’s national security adviser; and Homeland Security Secretary John F. Kelly, another retired four-star Marine general.

Mattis and Dunford usually dine with Trump once a week, sometimes in a group, sometimes one-on-one, the official said.

“The president does respect the chain of command, and he gets the vast majority of his information from the top echelons of his national security teams,” the official said.

The generals running the wars — Lt. Gen. Stephen Townsend in Iraq and Gen. John W. Nicholson Jr. in Afghanistan — are “three or four echelons below” the president, the official said.

It hasn’t taken long for ground commanders to exercise their newfound freedom under Trump — and for it to backfire.

In April, Adm. Harry B. Harris Jr., the Pentagon’s top commander in the Pacific, announced that he had ordered the aircraft carrier Carl Vinson and its escort ships to detour north from Singapore to North Korea amid rising tensions with the nuclear-armed regime.

Trump quickly boasted that an “armada” was racing toward the Korean peninsula. The Pentagon was left scrambling a week laterwhen it emerged that the Carl Vinson had instead sailed south to conduct exercises in the Indian Ocean. Harris later apologized to Congress for the confusion.

Nicholson similarly surprised the White House when he authorized use of the so-called mother of all bombs against an Islamic State tunnel complex.

Harris and Nicholson had the authority to make those decisions under Obama. But it’s unlikely either would have taken such action without seeking White House approval, according to officials.

The risk of Trump’s hands-off policy, at least for the Pentagon, was clear when he seemed to accept no responsibility after a U.S. military raid in Yemen that he had authorized nine days after he took officewent awry. He instead appeared to blame “the generals” for the death of Navy SEAL Chief Petty Officer William “Ryan” Owens in the Jan. 29 raid, which also killed more than a dozen civilians, including women and children.

Anthony Cordesman, a former intelligence director at the Pentagon now with the Center for Strategic and International Studies, a Washington think tank, said the military will carry out tactics to execute a president’s policy but cannot develop its own policy.

“Military operations should not be micromanaged but they cannot go unmanaged either,” he said. “A president has to take responsibility for his own policy and overarching strategic goals. That is not something that can be delegated.”

william.hennigan@latimes.com