There’s an old military adage that no battle plan survives first contact with the enemy — and the need to adapt on the fly applies to military exercises such as Rim of the Pacific as well.

The 844-foot amphibious assault ship USS Bonhomme Richard, the flagship for Combined Task Force 176 during RIMPAC, was still pierside at Pearl Harbor on Tuesday morning, five days after the big international interoperability exercise ended.

Most, if not all, of the visiting RIMPAC ships already had departed.

The Bonhomme Richard experienced a propulsion problem and spent the second half of the monthlong exercise in port, U.S. Naval Institute News reported.

An amphibious assault ship operates with a crew of over 1,000, according to the Navy.

“Although pierside, USS Bonhomme Richard was still a RIMPAC participant,” Lt. Rochelle Rieger, a spokeswoman for the Navy’s 3rd Fleet in San Diego, said in an email Tuesday.

3rd Fleet plans and runs RIMPAC, which was mainly held in Hawaii but also in Southern California.

Royal Australian Navy Commodore Ivan Ingham, the Combined Task Force 176 commander, still maintained command and control over RIMPAC amphibious units from the pierside Bonhomme Richard, Rieger said.

Asked what was happening to fix the San Diego-­based ship, Rieger said, “As a matter of policy, we do not discuss future ship operations or specific repair plans.”

The Pearl Harbor submarine USS Olympia found itself itself in a position to fire a torpedo tube-launched Harpoon anti-ship cruise missile — a first for a submarine in 20 years — and an Mk-48 heavyweight torpedo.

The Harpoon was planned for July 12, and the torpedo was not.

The Australian sub Rankin was scheduled to fire an Mk-48 torpedo to sink the decommissioned ship Racine, but it was in port for maintenance July 12 and the Los Angeles-class submarine Olympia was called upon at midday to fire the torpedo, the Navy said.

The live firing of a Long Range Anti-Ship Missile from an Air Force B-1 bomber also was scheduled for July 12. The only information reported was that the mission was delayed.

The Army, meanwhile, used a Gray Eagle drone to observe the target ship and pass the information to AH-64 Apache helicopters when it was determined that a Japanese P-3 Orion surveillance and reconnaissance plane couldn’t communicate with U.S. forces.

“Maritime forces are inherently flexible,” Rieger said. “RIMPAC provides realistic, relevant training that increases participants’ abilities to plan, communicate and conduct complex maritime operations efficiently and effectively no matter what the condition or situation.”