EU Defence HQ: From economic integration to common Military Force
"We don't have a permanent structure and without that, we are not able to work efficiently and so we must have a European HQ and... work towards a common military force," Juncker told the European Parliament in his annual State of the Union address.
The speech was dominated by Britain's shock June vote to quit the European Union, depriving it of a major, nuclear-armed NATO military power but one which had also been hostile to any suggestion the bloc should have its own army.
Juncker stressed that post-Brexit, the EU's remaining 27 member states had to stick together and that included taking on increased responsibility for their defence.
"We can no longer depend on the power of individual member states and together we have to make sure we protect our interests," he told MEPs.
Twenty-two of the EU's 28 member states are also members of the US-led NATO alliance, headquartered in Brussels, but Juncker insisted the bloc's military ambitions would not undercut this key relationship.
"This should be complementary with NATO -- more European defence does not earn less transatlantic solidarity," he said.
Juncker gave no further details although it is expected that any such EU military HQ would also be based in Brussels, home to all its major institutions.
As well as an increased military role, Juncker also said the EU will have to step up its diplomatic presence, suggesting the bloc should have a single foreign minister.
Current foreign affairs head Federica Mogherini was doing a "remarkable job" in promoting peace in Syria but backed up by the member states, she should now have a seat at the negotiating table, he said.