The last time an Arab-led force marshaled armies from across the region against a common enemy –- Israel -- the result was a resounding defeat that would shape the Mideast for decades to come.
Now, nearly 50 years later, Arab states are joining forces again -- this time, with the immediate aim of restoring order in chaotic Yemen, and moving as well to quell other regional conflicts.
But analysts say the nascent military alliance, whose planned formation was announced over the weekend by Arab leaders meeting in Egypt, could usher in new regional crises and intensify existing ones, sharpening sectarian differences between Sunni and Shiite Muslims and complicating already tangled national conflicts.
Yemen, whose tribes have for centuries been hostile to outsiders, could prove a deadly quagmire if conventional infantries from elsewhere in the Arab world attempt to wage a ground war against a homegrown, battle-hardened guerrilla force, the Shiite Muslim Houthi rebels. And a momentary sense of unity among Arab comrades-in-arms may fade as their sometimes-conflicting agendas come to the fore.
Saudi Arabia, the Persian Gulf's Sunni powerhouse, has to some extent preempted the Arab League's weekend call for the creation of a regional military task force –- whose specifics are not yet clear -- by assembling a coalition to support its air war in Yemen. On Monday, its warplanes pummeled Houthi positions across the country for a fifth straight day.
Terrified civilians fled the capital, Sana, amid thunderous bombardment, and dozens of displaced people were reported killed as they sheltered in a camp in Yemen's northwest, near the Saudi frontier.
The Saudi-led bombing campaign, joined by Gulf allies and supported by the United States, among others, is aimed at halting a Houthi advance on Aden, the southern port city that is Yemen's main commercial hub, and securing the 1,000-mile Saudi border with Yemen. The security of shipping lanes that lie along the Yemeni coast is also a key concern for Saudi Arabia, one of the world's leading oil producers.
But direct Saudi military involvement has already rendered the Yemen conflict more overtly sectarian, emphasizing its character as a growing proxy war. The Houthis, adherents of the Shiite offshoot Zaidi sect, are aligned with Shiite Iran, the Saudis' main rival for regional influence. The Houthis and other Shiites are considered heretics by some Sunni groups.
Egypt is believed to have carried out the first naval bombardment of the Yemen conflict on Monday, reportedly striking a Houthi column outside Aden from warships offshore. The government of President Abdel Fattah Sisi is deeply beholden to Saudi Arabia for the financial lifeline extended by it and other wealthy Gulf monarchies, and Sisi, a former military man, is eager to bolster Egypt's status as a regional military shield.
There is an inherent internal contradiction, however, to the Saudi-Egypt axis: Sisi describes the threat of terrorism -- by which he, in large measure, means his main domestic opponent, the
"The Saudis started the strikes days before the (Arab League) summit so it would not look as if they needed a formal consent from Egypt," Egyptian political analyst Mustafa Ellabbad wrote in the pan-Arabic daily newspaper As-Safir, based in Beirut. "They are trying to shrink Egypt's influence on the Yemeni conflict to a minimum."
And whereas Sisi spoke of Arab nationalism as galvanizing the creation of an Arab interventionary force, Ellabbad wrote, Saudi Arabia's recently crowned King Salman "set his first priority, which is Iran as an enemy."
Efforts to foster regionally led miliary cooperation date back to the Arab League's founding in 1945. But in 1967, the armies of Egypt, Syria and Jordan suffered an epic and humiliating defeat when they tried to stage a three-pronged attack on Israel.
Egypt and Syria, aided by other Arab states, were beaten back again in 1973, setting in motion the process that culminated in Israeli peace treaties with Egypt and Jordan.
Since then, regional military efforts have largely come under outside leadership, as in the 1991 U.S.-led war against Iraq to free Kuwait. Even then, large-scale Arab participation had something of a cosmetic element, with American troops doing battle to clear out the bulk of the Iraqi forces. It set the stage for a ceremonial "liberation" by Arab militaries, though Arab troops were also involved in the fighting.
More recent joint actions have been limited in scope, such as Egypt lending support last year to the United Arab Emirates for strikes on Islamist armed groups in Libya.
Even urgent threats at their very doorstep do not always galvanize a robust armed response from governments in the region. It fell to the Obama administration last year to prod Arab states into a U.S.-led coalition to confront the Sunni militants of Islamic State, even as the group seized large swaths of Iraq and Syria, enforcing its writ with a reign of terror and establishing loose allegiances with militant groups across North Africa.
In Yemen, the current Saudi-led air war could be a prelude to a far messier phase, many commentators predicted. Yemen's rugged geography -- and the Houthis' intimate knowledge of it, coupled with a nimbler guerrilla style of fighting -- could confound foreign infantry troops, analysts said.
"It could turn into a trap for ground forces," wrote Adel Hammouda, editor-in-chief of the Egyptian independent weekly Al-Fagr.
In Yemen, many people are torn between a violent distaste for foreign intervention -- even from fellow Arabs -- and a desire to crush the Houthis once and for all. The group has staged previous uprisings, but none that so seriously imperiled Yemen's status as a functioning state.
"I am against the Houthis, but at the same time against outside interference," said Mona Shami, a jobless graduate who blames the rebel movement for exacerbating hardships in what was already the Arab world's poorest country. "There has to be some middle way."
Special correspondents Zaid Al-Alayaa in Sana and Amro Hassan in Berlin contributed to this report.