The Saudi-led coalition's air strikes and a possible ground invasion of Yemen to defend President Abedrabbo Mansur Hadi from Huthi rebels transcend the achievements that the conflicting parties would make in the battlefield. Their importance lies in the recalculations that the region's players would make after the operation that was launched by Riyadh last month.

The move of Saudi Arabia and its allies against the Shiite rebels was a form of “revolution” in the policies of Riyadh and Gulf countries amid the turmoil in the region and against the expansion of Iranian influence in more than one state.

Across the Middle East, fierce rivalry between Sunni Saudi Arabia and Shiite Iran is heightening sectarian tensions, even in conflicts that analysts say are primarily political.

Riyadh and Tehran adhere to different branches of Islam and have often backed members of their own sect in regional conflicts.

Nael al-Sharif is working on an extension to his property in the Jalazon refugee camp in the Israeli-occupied West Bank. But he is not building outwards -- instead he's expanding upwards.

In many of the Palestinian camps, which have evolved down the decades into densely populated areas teeming with narrow alleyways, families that cannot afford to buy new land simply add floors to existing property.

Iran's ties with its Arab neighbors across the Gulf have long been strained but one nation -- Oman -- has carved out a unique and potentially crucial relationship with Tehran.

From Syria and Iraq and now the conflict in Yemen, Sunni Arab states led by Saudi Arabia have vied with Shiite Iran for influence in the Gulf and the greater Middle East.

The framework nuclear deal sealed by world powers and Iran leaves major questions: Could Iran cheat? Possibly. Would the U.S or anyone else be able to respond in time? In theory, yes. Are they prepared to use military force? Questionable.

Would a final deal settle global fears about Iran's intentions? Almost surely, no.

The explosion of Yemen's war proved that the conflict in the region is no longer interpreted by wars and disputes in Lebanon, Syria, Iraq and Bahrain, but an attempt by Iran to have a sway in Middle East policy in return for efforts by Gulf states and Egypt to limit Tehran's expansion.

Saudi Arabia and Egypt have given Iran two options after the military intervention by Sunni Riyadh against a Shiite rebellion aided by Tehran: Either it should stop its expansion in the region or face a total confrontation beyond the borders drawn by Iran.

The agreement at a weekend Arab summit to establish a joint military force has raised serious doubts about prospects of such a force becoming a reality on the ground, experts say.

Egyptian President Abdel Fattah al-Sisi announced the accord on Sunday at the end of the summit he hosted in the resort of Sharm el-Sheikh, setting a four-month timeframe for the 22-member Arab League to decide on the composition and rules of engagement of the joint force.

Sweden's foreign minister is hardly the first diplomat to raise concerns about Saudi Arabia's human rights record, but when she used the word "dictatorship" in a speech last month she crossed a red line for the kingdom at a time of intense regional turmoil, igniting a diplomatic crisis.

The harsh response from Saudi Arabia and its Gulf allies jolted Stockholm's standing in the Arab world, threatened its Gulf business interests and may have imperiled its bid for a rotating seat at the U.N. Security Council. The crisis also underscored the perils of promoting reform four years after the Arab Spring, particularly in Gulf monarchies that rode out the ensuing unrest by clamping down on dissent.

U.S. and Iranian diplomats gather at a Baroque palace in Europe, a historic nuclear agreement within reach. Over Iraq's deserts, their militaries fight a common foe. Leaders in Washington and Tehran, capitals once a million miles from each other in ideological terms, wrestle for the first time in decades with the notion of a rapprochement.

Yet the old adversaries are locked in a proxy war across an ever more volatile region. In Syria, the United States arms insurgents seeking to oust the Iran-backed government. In Lebanon, the Palestinian territories and elsewhere, Iran supports militant groups determined to end Israel's existence. And now in Yemen, the U.S. is backing a military intervention by Sunni powerhouse Saudi Arabia against a Shiite rebellion aided by Iran.

As the United States backs a Saudi-led intervention in Yemen, Washington runs the risk of undercutting its diplomacy with Iran and becoming embroiled in a regional sectarian conflict running from Aleppo to Sanaa.

Despite the risks, and with negotiations on Tehran's nuclear program at a crucial moment, President Barack Obama swiftly endorsed air strikes by a coalition of Gulf countries against Iranian-backed Huthi rebels in Yemen on Wednesday.