World militaries spent nearly $1.67 trillion on defense activities and equipment in 2015, an increase of 1 percent in real terms over the previous year and the first uptick since 2011, according to the Stockholm International Peace Research Institute (Sipri). Saudi Arabia overtook Russia as the third biggest-spending nation behind the U.S. and China, but this was mainly due to the decline in the value of the Russian ruble, the institute said.

Sipri released its latest report on world military spending on April 5. The Swedish think tank counts as military expenditures all government spending on defense forces and activities, including salaries and benefits, operational expenses, arms and equipment purchases, military construction, research and development and administrative costs.

The total expenditure on defense in 2015—equivalent to 2.3 percent of global GDP—reflects continuing growth in military spending in the Asia-Pacific region, central and eastern Europe and some Middle Eastern states. A recent decline in spending by western nations is leveling off, Sipri said. Meanwhile, spending decreased in Africa, Latin America and the Caribbean.

“On the one hand, spending trends reflect the escalating conflict and tension in many parts of the world; on the other hand, they show a clear break from the oil-fueled surge in military spending of the past decade,” said Sam Perlo-Freeman, head of Sipri’s military expenditure project. “This volatile economic and political situation creates an uncertain picture for the years to come.”

The top 15 spending nations remained the same from 2014, but the order of some nations changed. The U.S. ($596 billion) and China ($215 billion) retained their top positions. Saudi Arabia ($87.2 billion), which led an intervention of Yemen’s civil war last year, moved from fourth place to third, but at a slower rate of growth than before due to the sharp decline in the price of oil, which underwrites government spending. Oil prices also curbed the rate of spending by Russia ($66.4 billion), which dropped to fourth place. Nevertheless, despite falling revenues from crude oil sales, Saudi Arabia and Russia recorded their highest levels of military spending as a share of GDP since 1990, respectively 13.5 percent and 5.4 percent.

The decline in the value of the euro was a major factor behind the UK ($55.5 billion) climbing into fifth place above France ($50.9 billion), which dropped beneath both the UK and India ($51.3 billion) into seventh place. The value of the euro also helped Japan ($40.9 billion) take over eighth place from Germany ($39.4 billion), which fell to ninth.

South Korea was again the tenth biggest spending nation at $36.4 billion last year, followed by Brazil ($24.6 billion), Italy ($23.8 billion), Australia ($23.6 billion), UAE ($22.8 billion) and Israel ($16.1 billion).

The U.S. is ensconced as by far the biggest spending nation, although its annual expenditure declined by 2.4 percent last year, its slowest rate of decline in four years, Sipri said. Since its most recent peak in 2010, U.S. military spending has decreased by 21 percent, due to the withdrawal of most American troops from Afghanistan and Iraq and the impact of the 2011 Budget Control Act, which imposed mandatory budget cuts on federal agencies. However, the impact of those cuts was mitigated with targeted legislation in 2014 and 2015.

In a selected acquisition report the U.S. Department of Defense (DOD) released in March, the Pentagon reduced the total estimated development and acquisition cost of its largest procurement—the Lockheed Martin F-35 Lightning II—by $12.1 billion to $379 billion for 2,443 jets. (The cost of developing the fifth-generation fighter, a phase that is expected to end in 2017, is $55 billion.)

However, the DOD has also stretched the planned service life of the F-35 by 1.6 million flight hours and six years to 2070, with production slated to run through 2038. This has resulted in a $107 billion increase in the program’s estimated operations and support cost to $1.12 trillion—bringing the total cost of building, flying and maintaining the F-35 to $1.5 trillion.