For the first time since 1998, global military spending is down. This coincides with a major decline in U.S. spending, which fell by more than $40 billion between 2011 and 2012. Even with this decline, however, the United States still had a military budget four times larger than China, the next biggest spender.

The Stockholm International Peace Research Institute (SIPRI) measures annual military spending for most of the world’s armed countries. According to SIPRI, the United States spent $668 billion, more than the combined budgets of the next 10 countries. While the U.S. budget has declined, some of the other global powers, including Russia and China, have ramped up spending. Based on SIPRI’s 2012 data, these are the countries spending the most on the military.

Click here to see the countries spending the most on the military

The major decline in the U.S. military budget was the result of two factors, explained Carina Solmirano, senior researcher at SIPRI’s Military Expenditure and Arms Production Programme. The first is the severe decline in overseas military spending after America’s eight-year war in Iraq ended in 2011, as well as the continued wind down of operations in Afghanistan, Solmirano said.

“The second reason,” said Solmirano, “is purely economics. … The United States is facing a huge deficit crisis, and as part of the agreements in 2011 and 2012, the Department of Defense agreed to start a reduction of expenditure — quite a significant reduction.” Solmirano added that barring the emergence of a new conflict, U.S. military spending likely will continue to fall.

Short-term changes in military spending, like the nearly 6% decline in the United States, often go hand-in-hand with periods of economic growth or crisis. Indeed, spending among nearly all the top European military powers, including Italy, France and the United Kingdom, declined last year.

Meanwhile, China went against the global trend by increasing its spending by nearly 8% between 2011 and 2012, and by more than 47% since 2008. Part of this increase is for geopolitical reasons, explained Solmirano, who added the increase in spending has “been parallel to its increase in economic power as well.”

Other nations, while not the biggest spenders overall, have much larger military budgets relative to the size of their economies. As of 2012, the United States spent 4.4% of its gross domestic product (GDP) on the military. In countries like Saudi Arabia and Oman, military costs amounted to more than 8% of GDP. Part of this, explained Solmirano, has to do with the consistently tense security situation in the Middle East. She added that countries like Saudi Arabia are able to fund massive militaries with substantial oil revenue.

24/7 Wall St. reviewed the 10 countries that spend the most on their military in 2012, based on SIPRI’s measure of military spending in more than 130 nations. We also reviewed SIPRI data on military exports and imports, as well as military expenditure as a percentage of GDP. From Globalfirepower.com, we reviewed statistics on military size and strength, based on the most recent available data. We also considered GDP and GDP growth figures from the International Monetary Fund (IMF).