Britain has been overtaken in military spending by a Saudi Arabia empowered by United States military aid, a new report has revealed.

Military Balance 2014, produced by the International Institute for Strategic Studies (IISS) think-tank, has revealed that in 2013, the United Kingdom slipped into fifth place in the world rankings behind the United States, China, Russia, and Saudi Arabia.

While Britain has been shrinking its defense budget in recent years in line with “government austerity” measures, Saudi Arabia’s military spending was burnished by U.S. Foreign Military Assistance, meaning that in 2013, the UK spent just $57 billion against Saudi Arabia’s $59.6 billion.

Qatar, Saudi Arabia, and the UAE have all bought, or are buying, Western missile and air defense and strike systems, which may explain the sudden uptick in spending in the region.

In 2012, the UK was ranked third behind the United States and China, a position now occupied by Russia.

However, Britain’s decline may be little more than an exchange rate fluctuation, explains IISS: “If sterling-dollar exchange rates from last week were applied to UK defence spending levels instead, these would rise from US$57bn to US$61.1bn in US dollar terms, above Saudi Arabia and into fourth place.”

The same applies to Japan’s place in the rankings, which at first looks like a decline in Japan’s military capability. In reality, its six-fold drop to $51 billion is explained by a depreciation in the value of the Japanese currency, yen.

The United States remains the largest spender in the world, with over $600 billion spent on defense last year. The second closest, China, only spent $112 billion, though the Chinese are growing their defense budgets, while America’s is technically shrinking.

IISS researchers have claimed that if Chinese military spending continues to increase at its current pace, the country may well overtake the United States sometime in the 2030s. It may however take the Chinese much longer to match America’s overall military capabilities, they clarified.