The chaotic withdrawal of Western forces from Afghanistan is still troubling for many U.S. allies.
And at a summit of European Union leaders this week, the problem has been laid bare.
The EU is divided over the bloc's reliance on the United States for its defense strategy.
Reuters diplomatic sources say that the EU has failed to resolve their debate over whether to develop an independent defense force.
Leaders meeting over dinner in Slovenia on Tuesday (October 5) split rather predictably into eastern states fearful of Russia who want to strengthen Europe within NATO, and those led by Germany, Italy, Spain and France, who want a more robust EU capability.
Before the closed-door discussions in Brdo Castle, French President Emmanuel Macron told reporters that the 27-nation bloc must do more to manage crises on its borders and to be responsible for its own security.
He had questioned the reliability of the U.S.'s protection of Europe prior to last month's dispute over an Indo-Pacific pact, which has added fuel to the fire.
The diplomatic crisis was triggered after the United States negotiated a military accord in secret - known as AUKUS - tightening its military cooperation with Australia and Britain to counter China, but excluding France.
The EU leaders are also being joined by six Balkan leaders - part of the bloc's decades-long strategy to create a "ring of friends" from southeastern Europe to North Africa.
Proponents of a stronger EU defense say the warnings have been many, including Washington's so-called"pivot to Asia" during the Obama administration, Britain's departure from the bloc, and the Trump administration's "America first" policies.
But despite progress on building a common defense fund to develop weapons together, the EU has yet to deploy its battalion-sized battlegroups in a crisis.