The leaders of Saudi Arabia, the United Arab Emirates, Kuwait, Qatar, Oman and Bahrain announced the move, including the formation of a 100,000-strong joint defense force, in Dubai at the end of the GCC's annual summit in December.
The GCC has been talking about a joint defense network pretty much since the alliance was formed in 1981, at the start of the 1980-88 war between Iraq and Iran, with security and economic development its primary objectives.
But nothing substantial ever has emerged because of the deep-rooted rivalries between the ruling families of the Arab states in the gulf. Primarily, the smaller states are reluctant to submit to Saudi Arabia's dominance.
Threat perceptions differ. The Saudis shudder over Iran, their longtime rival for regional leadership, while Kuwait worries about Iraq, its northern neighbor, which under Saddam Hussein invaded the emirate in August 1990 and triggered a regional war.
And there's little expectation among military analysts and longtime observers of the region that anything will come of this latest effort even though it was a decision driven in part by growing concerns the United States is scaling back its Middle East commitment and seeking a rapprochement with Iran.
The GCC decision was "largely Saudi-driven given their geopolitical predicaments," observed Frederic Wehrey of the Carnegie Endowment's Middle East Program.
Michael Knights of the Washington Institute for Near East Policy noted: "I expect Qatar and Oman will be the ones to most diverge, and Kuwait probably next. Some won't participate, some will withdraw. It will be a fractured union."
The overwhelmingly Shiite Islamic republic is the main rival of the Sunni-ruled GCC states, who are deeply suspicious of the Tehran regime's newfound moderation.
Analyst Matthew Hedges, based in the United Arab Emirates, said the GCC summit's endorsement of a joint command, plus the establishment of a Gulf Academy for Strategic and Security Studies in the Emirates, is aimed at strengthening military cooperation among GCC states.
"The academy will look to increase knowledge transfer and greater comprehension of a unified realization of threats across the entire GCC region," said Hedges, who is with the Institute of Near East and Gulf Military Analysis in Dubai.
"There will be an initial focus on missile defense, border security and counterterrorism."
But even he is dubious about how effective the new GCC policy will be in the short term. Real interoperability "will take at least years to come to fruition."
The Americans, defenders of the gulf states for the last 40 years, have long preached joint missile defense, clearly aimed at countering Iran's growing arsenal of intermediate-range ballistic missiles and other such systems.
There's been little consideration of interoperability of the weapons systems and other equipment these states have acquired, largely a mix of U.S., British, French and even Russian hardware. Even the communications systems are not particularly compatible.
But it's only in the last couple of years, as the Iranian threat grew, that the GCC's key military powers, Saudi Arabia and the UAE, have moved in that direction.
And while the U.S. has racked up more than $100 billion in sales of increasingly advanced systems, weapons that until a couple of years ago were blocked because they could be used to threaten Israel, the GCC states still lack a cohesive defense network.
U.S. Secretary of Defense Chuck Hagel visited the gulf in December to reassure the monarchs of continued U.S. support.
But what he stressed was the need for greater cooperation through which the United States would sell weapons to the GCC states as a single military power rather than separate states pursuing individual procurement policies that did not promote close coordination on defense.
"Nothing's really different about this particular announcement" by the GCC summit, Knights observed.
There have been other ambitious plans announced over the last decade "without much to show for them," he said.
"There are real barriers to real gulf cooperation on the military front: capacity and political will," said Wehrey. "Any type of international or regional military coalition is increasingly complex."