In the early 1920s, the British protectorate of Kuwait held about two-thirds more land than it does today. At the Uqair Conference in 1922, the British high commissioner in Iraq Percy Cox gave much of southern Kuwait to the Najd Sultanate, which would later become the Kingdom of Saudi Arabia. Kuwaiti leadership was unhappy, but borders in the Arabian Peninsula then were relatively flexible.

While borders have hardened in the years since, the area between Kuwait and Saudi Arabia has remained undefined, even in 1938 when oil was discovered in southern Kuwait. The “Divided Zone” is an undefined 2,228 square mile, oil-rich area that straddles the two countries’ border and extends into the Persian Gulf. For years, the two states have coordinated and equally shared the profits from oil production here.

But in 2009, a new dispute emerged between Kuwait and Saudi over the Divided Zone. The two nations regularly refer to their relationship as “brotherly.” But the dispute triggered fears of some in Kuwait that Saudi Arabia might flex their muscles and redraw borders once again.