The size of the Army should not fall below 450,000 active-duty troops and 530,000 reservists for the foreseeable future, according to a long-awaited report by a congressionally appointed commission.
In addition, the Army should add an armored brigade back to Europe and leave an aviation brigade in South Korea, the commission said.
The report, which Congress ordered after the service drafted plans to reduce its forces to 420,000 troops by 2021, will provide defense hawks with ammunition in the fight against fiscal conservatives and liberals who want to cut defense spending.
"An Army of 980,000 is the minimally sufficient force to meet current and anticipated missions at an acceptable level of national risk," said an executive summary of the report by the National Commission on the Future of the Army.
The commission included former senior Army and Pentagon leaders, including retired Gen. Carter Ham, former assistant secretary of the Army Thomas Lamont, retired Sgt. Maj. Raymond Chandler, retired Gen. Larry Ellis, former Pentagon comptroller Bob Hale, former deputy under secretary of defense for policy Kathleen Hicks, retired Lt. Gen. Jack Stultz, and retired Gen. James D. Thurman.
The Army is in the midst of a massive downsizing, from a high of 1.1 million members in 2012 to 980,000 by 2018. The downsizing is due to a post-war drawdown as well as defense cuts mandated by Congress.
The 2011 Budget Control Act required $500 billion in defense cuts over a decade, on top of $487 billion already planned.
Last year, lawmakers reached a two-year agreement that would reduce the level of cuts for 2016 and 2017, but the cuts are slated to return in 2018.
If the cuts remain in place, the Army may still reduce to 420,000 personnel, defense officials have warned, which is a level smaller than pre-World War II.
When the plan to reduce troop levels to 420,000 was drafted, that did not take into account a "sizable continuing force" in Afghanistan, ISIS and a resurgent threat from Russia, said Chandler.
The commission also weighed in on a fight between the active-duty Army and the National Guard over Apache attack helicopters.
As part of the downsizing, the Army is retiring its armed Bell OH-58 Kiowa helicopters and wishes to transfer all of the National Guard's Apaches to the active-duty forces, a move that would save the Army $12 billion but is opposed by the National Guard and some members of Congress.
The commission recommends allowing the Guard to retain four Apache battalions of 18 helicopters each, which would surge to 24 helicopters during deployments.
That recommendation would cost the Army $165 million a year, and a one-time procurement cost of $400 million. To pay for the recommendation, the commission recommends slowing down purchases of and upgrades for existing Black Hawk helicopters.
Army officials say if the Guard retains any Apaches, it would force the active-duty side to build new ones from scratch, at $40 million each.
But the commission said "keeping attack helicopters in the Army National Guard is important in meeting a key Commission goal of achieving one Army that works and trains together in peacetime and fights in war."
The commission also recommended permanently stationing an armored brigade in Europe, due to the threat from Russia, and stopping a move to reduce one combat aviation brigade from South Korea, due to the threat from North Korea.
In order to retain the extra combat aviation brigade, the Army would need to purchase 48 more Apaches, which would amount to about $2 billion to buy and cost $1 billion a year.
Commission members anticipated the Army would blanche over some of the recommended additional costs, but said the security environment calls for the measures.
"The equilibrium is not right when you look at supply and demand," Thurman said.
The Army thanked the members of the commission for their insights and hard work.
"We are currently assessing the report and expect its recommendations to provide opportunities to strengthen the effectiveness of our force," said Army Chief of Public Affairs Brig. Gen. Malcolm Frost in a statement.
But retired Army Lt. Gen. Dave Barno, an Atlantic Council non-resident fellow, said the commission "largely missed its primary if unstated task: healing the deep rift between the active Army and the National Guard."
"But beyond preserving four Apache battalions in the Guard, they offer few other substantive suggestions on how to truly integrate active, Guard and reserve capabilities into a unified force," he said in a statement.
Nora Bensahel, a co-nonresident senior fellow at the Atlantic Council said the commission missed an opportunity to provide fresh thinking on integrating the active Army, National Guard and the Reserve.
"These blended units have great potential to improve the capacity and readiness of the force, as well as promote a one-Army culture," she said.
This story was updated at 5:28 p.m.