WASHINGTON — The Pentagon on Monday requested its largest-ever investment in innovation and next-generation weapons as part of a $705.4 billion budget proposal for fiscal year 2021, as the United States eyes increased military capabilities by its great-power competitors, China and Russia.

The Defense Department unveiled its 2021 budget request as part of the White House’s $4.8 trillion federal spending proposal for next year that would cut social programs while investing heavily in national defense. The proposal would provide a total of $740.5 billion for defense spending, which includes the Pentagon’s budget as well as funding for nuclear programs within the Department of Energy.

The request includes funds to build up the military’s newest service, the U.S. Space Force, to buy dozens of aircraft, ships and land vehicles, and a proposed 3% boost in troops’ pay. It would represent a slight increase to the $704.6 billion that Congress provided the Pentagon for fiscal year 2020. Lawmakers also provided the Pentagon an extra $8 billion of emergency funding this year to rebuild installations hit by natural disasters in recent years, including hurricanes and major floods.

While the proposed budget largely looks to the future, it provides funds for ongoing combat operations in Afghanistan, Iraq and Syria and training missions in Europe — all at lower levels than in fiscal year 2020. The budget predicts smaller troops presences worldwide, presuming a reduction of nearly 8,000 troops to operations around the globe.

But the underlying theme of the request is to prepare the military to fight the next war that the Pentagon’s top planners anticipate, which is a major conflict against a nation-state with similar military capabilities to the United States, senior defense officials, who spoke on condition of anonymity, said Friday. It is the second consecutive budget crafted based on the Pentagon’s 2018 National Defense Strategy, which shifted the department’s primary focus to great-power competition with Russia and China over the threat of international terrorist organizations that the United States has fought for nearly two decades.

That means new technology. The request includes $106.6 billion for research, development, testing and evaluation of the modern weapons systems required to fight such a war, including $3.2 billion meant to hasten the development of hypersonic weapons, $1.5 billion for the development of 5G communications technology that officials said is critical to ensuring systems and troops can share information rapidly, $1.7 billion earmarked for automation research, and another $800 million for Pentagon organizations developing artificial intelligence capabilities.

It also means strengthening the three-legged U.S. nuclear deterrent, which the officials touted as the nation’s foundation for preventing a major attack by another power. The proposal seeks a 20% boost in spending on upgrades to the Pentagon’s aging nuclear triad and pouring nearly $30 billion into ongoing projects. Those projects include $4.4 billion for the Navy’s future Columbia-class, ballistic-missile submarines, which is scheduled to begin construction next year, $2.8 billion for the Air Force’s future B-21 Raider bomber, which is scheduled to begin flying in 2022, and $1.5 billion for the Ground Based Strategic Deterrent, the replacement for the decades old Minuteman III intercontinental ballistic missiles, expected to be completed in the late 2020s. It also includes some $110 million toward a program to make some versions of the Air Force’s F-35A Lightning II fighter jets nuclear capable. That is expected to occur by fiscal year 2024.

The budget also invests heavily in space and cyber capabilities. It includes $18 billion for space, which would grow the Space Force, improve space-based missile warning capabilities, improve GPS systems, reduce the risk of satellite communications jamming and conduct three space launches. It would also spend nearly $10 billion on cyber programs to improve offensive and defensive capabilities and bolster cybersecurity for Defense Department networks, systems and information.

While the budget is similar in scope to the fiscal year 2020 budget, and Pentagon officials foresee near-flat budgets well into the future, it proposes moving funding in older technology and non-military functions into warfighting coffers.

The officials said the Pentagon was forced to “make difficult choices,” proposing to end investment in some aging but useful platforms, including KC-135 and KC-10 airborne tankers, B-1 bombers, F-15C fighters and cutting four Navy cruisers.

Budget officials also looked for savings within the Pentagon’s so-called Fourth Estate, the non-warfighting agencies and activities— including Stars and Stripes — that are not assigned to a military service. After a review, officials proposed moving some $5.3 billion in funding from these organizations to areas that contribute directly to “lethality.”

The decisions, these officials said, were aimed at deciding “what is useful for the high-end fight.”

Though lawmakers ultimately fund their own priorities when allocating the Pentagon’s budget, the yearly budget proposal outlines the Pentagon’s top priorities for the coming year. It is the first budget proposal released under Defense Secretary Mark Esper and Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, who both assumed their roles last year.

The Pentagon’s budget proposal would allocate $178 billion for the Army, $161 billion for the Navy, $46 billion for the Marine Corps, $191.8 billion for the Air Force and $15.4 billion for the Space Force.

It would boost the U.S. military’s end strength with 5,600 new troops, bringing the total force to 2,153,500 troops, including active duty, reservists and National Guard members.

The 3% pay boost proposed for troops follows the 3.1% pay raise approved by Congress for them this year. The budget proposal also includes a 3.8% boost for basic allowance for housing and a 2.8% increase for subsistence allowance.

Among current weapons systems, the 2021 budget proposal invests heavily in airpower, as it did in 2020, while scaling back slightly its investment in shipbuilding.

The Pentagon aims to spend nearly $60 billion on aircraft in 2021. That includes $15.1 billion for fighter jets — 79 F-35 Lighting II advanced fifth-generation fighters, 24 F/A-18E/F Super Hornets and 12 F-15EX Advanced Eagles. It would also spend $3 billion on 15 KC-46 aerial tankers and $1.2 billion on AH-64E attack helicopters.

The budget proposal calls for $20 billion for ship building in 2021, down about $4 billion from 2020, even as service officials continue to support legislation directing the U.S. fleet to grow from 298 ships in 2020 to 355 by 2030. The funding would allow the Navy to reach 306 in 2021.

The 2021 proposal calls for a modest investment in ground systems. It would spend $1.4 billion on 4,247 Joint Light Tactical Vehicles, the Army and Marine Corps’ replacement for their aging Humvees. It would also spend $521 million to purchase 72 amphibious combat vehicles for the Marines. It would spend $1.4 billion to upgrade 89 M-1 Abrams tanks, and it would spend almost $850 million on upgraded Stryker armored vehicles.

The senior defense officials declined to discuss their criteria for determining how much funding would be provided for ongoing military operations in Afghanistan, Iraq, Syria and in Europe, where the U.S. troops partner with European allies to train in an effort to deter Russian aggression on the continent. But the budget proposal documents show cuts to spending on these operations.

The primary Overseas Contingency Operations account — money earmarked for wartime and other overseas missions — would be cut by about $12.9 billion to a total of $53 billion for 2021. It includes a $3.2 billion cut to fund the ongoing wars in the Middle East and Afghanistan, but the documents do not specify what would actually be reduced. It also would decrease funding for the European Deterrence Initiative by $1.5 billion, to $4.5 billion for next year.

The proposed budget envisions a drop in force levels on temporary deployments in the Middle East, Afghanistan, Europe and other locations from more than 99,000 in 2019 to just more than 91,000 last year. The officials said predicting such troop levels is difficult in any given year.

They expected such a troop reduction globally in 2019, but tensions with Iran actually produced an increase in the number of deployed troops globally, as the United States shuttled tens of thousands of new troops into the Middle East through 2019 and early 2020.

dickstein.corey@stripes.com

Twitter: @CDicksteinDC