U.S. Army leaders mapped out a rough plan to lawmakers Thursday describing how the service has spent the past 18 months preparing for war with North Korea.

Members of the House Appropriations Committee's defense subcommittee expressed a keen interest in possible contingency plans should the proposed summit between U.S. President Donald Trump and North Korean leader Kim Jong-un fail to result in an agreement over that country's nuclear weapons program.

Army Chief of Staff Mark Milley said the Army has conducted "a significant amount of training for contingency operations ... both on the peninsula itself with units that are stationed there but also with the units" in the U.S. Pacific Command area of operations.

"We've got, roughly speaking, 70,000 Army soldiers in the PaCom AOR and another 30,000 depending on exercise schedules," he said.

"And then in the continental United States, I guess it was a year or 18 months ago, we gave out guidance to our units that we would designate selected units to increase their readiness training specifically oriented toward high-end combined-arms warfare -- not specific necessarily to Korea but although it would be applicable to Korea.

"And we have been running those units pretty hard, getting them to a much higher level of readiness," Milley added.

Rep. Harold Rogers, R-Kentucky, wanted to know if the Army has done anything to prepare for a short-notice operation on the peninsula.

"In view of the unusual activities in the last few months, i.e., North Korea, what changes have you made, if any, in preparation for what may come?" he asked.

Recently sworn-in Secretary of the Army Mark Esper told lawmakers the Army will "hope for the best but prepare for the worst."

Esper recently visited American soldiers and leaders stationed in South Korea to observe the readiness posture firsthand.

"I can tell you everyone is working hard to ensure we are ready, that we are doing what is necessary to strengthen the hands of our State Department, our diplomats if you will, and to make sure we have all options available for our decision makers," he said.

Milley told Rogers that he could not get into specifics about North Korea.

"Congressman, I don't want to do a cop-out, but I would like to actually come by and brief you in a classified session on the details of what we are doing," he said.

Aside from training, the Army has taken steps to ensure that "all of the prepositioned stocks are full up" and increased the "personnel fill for the units that are both there and the units that are expected to first to respond," he said.

The Army has worked closely with PaCom leaders as well as commanders on the ground in South Korea to ensure units are ready a number of possible missions, Milley said.

"We have done a tremendous amount over the last 12 to 18 months or so in preparation for any possible contingency, so that the president has the widest latitude of options if needed," he said.

Defense subcommittee chairwoman Kay Granger, R-Texas, said she plans to set a date for a classified briefing on North Korea, adding that "everyone on the subcommittee will be invited because I know we all have questions."

Rogers also asked why the Army is "requesting a huge increase in 155mm artillery shells" in the proposed fiscal 2019 budget.

The Army requested funding to buy 148,000 155mm artillery shells, compared to fiscal 2018's request to buy 16,500, he said.

"I'm an old 155mm artillery guy in the Kentucky Guard, so I have got an affinity for 155mm shells. What's going on here?" Rogers asked.

Milley said he wants to make sure the service has sufficient ammunition stocks of 155mm “because the United States Army has been and still is a fires-based Army in order to create opportunities for maneuver and movement, so artillery is fundamental to our ability to do that."

"And in the event of a contingency, artillery and munition consumption rates would be really high, so I want to make sure that the ammunition stockpiles are significant enough to withstand any contingency," he said.

-- Matthew Cox can be reached at matthew.cox@military.com.