Should Germany become a major military power? And will it happen?
With Vladimir Putin destabilising the east, Middle Eastern and Asian conflicts spurring new migration into Europe, and Donald Trump questioning US commitment to NATO, Germany has good reason to feel insecure.
Chancellor Merkel told Germans in May that "we must fight for our future ourselves as Europeans". German troops have been deployed in locations ranging from Lithuania to Afghanistan and Mali. And Merkel has promised to raise German defence spending.
But Germany and its Chancellor face a fundamental problem. Most Germans are very reluctant to go down this road.
They regard their own army with suspicion - an attitude reinforced by a recent scandal involving the Bundeswehr. Foreign deployments are tightly restricted by German law and parliament.
Above all, attitudes are shaped by the shadow of history.
So successful have outsiders been in demilitarising Germany - so sensitive are Germans about their warlike past - that today's greatest European power is likely to remain a battlefield weakling.
After World War Two, there was much debate about whether Germany should have any armed forces. An end had to be made, it was argued, to a cycle which began with Prussian militarism and ended in Nazi war crimes.
While communist-ruled East Germany did create a People's Army following German military traditions, in democratic West Germany - occupied by Britain, France and the US - a very different armed services emerged.
The Bundeswehr, born in the mid 1950s, was a deliberately modest force, meant only to defend West German territory, not fight abroad. Its recruits were taught to think of themselves as "citizens in uniform".
Indeed the uniform itself, says historian James Sheehan, "really does resemble [that of] bus drivers rather than the old guards' regiments".
Modern Germany, says Sheehan, "thinks of its military very much the way most states think of their police force".
What he calls a "persistent distrust of military institutions," he adds, "continues to be strong, and in some ways has become stronger".
Underlying all this is the enduring memory of the horrors of World War Two - not only the shame of Nazi crimes but also the devastation inflicted on civilians.
Werner Kraetschell, a Protestant pastor from an old Prussian family who became a military chaplain, speaks of many thousands of Germans growing up after the war "without fathers". That still prompts what he calls the "inner reactions" of Germans when it comes to military affairs.
For a long time, says military expert Sophia Besch from the Centre for European Reform: "If you were a soldier [in Germany] you could not really ride a train in your uniform. You'd be approached by passengers calling you a 'murderer'."
When the Cold War ended and Germany reunified, its people believed peace was now more or less permanent. But Christian Democrat politician and former defence minister Franz Josef Jung says "reality has caught up with us".
Yet he concedes that "our population has had an attitude shaped more by pacifism".
"We have to make clear," he argues, the need for new policies to "overcome internal and external security challenges".
Since reunification Germany has begun to deploy troops abroad for the first time. But the sensitivities are acute.
In 2009 there were allegations of a cover up following a military strike in Afghanistan involving German forces that caused civilian deaths. Dr Jung was forced to resign as a minister.
Parliamentary supervision of any deployment is intense - with the Green party among the most critical. Doris Wagner, Green MP and security specialist, says she wants to keep the idea of Germans being "more restrained in military action".
Meanwhile the old idea of a citizens' army has struggled to survive. Germany has abolished conscription and is concentrating, like other modern armies, on smaller specialist forces.
And old angst about the military revived last month when a scandal exposed far right infiltration of the Bundeswehr - including an alleged terror plot to murder asylum seekers and celebration of Nazi-era traditions.
Some said the problem was exaggerated in a fevered atmosphere. But it shows, says Sophia Besch, "that there's still a really tortured relationship between the Bundeswehr and the German public".
There is now real urgency in the German debate about its military future.
Donald Trump's claims that NATO is "obsolete" and his broader questioning of collective security has been a "big surprise" to Germans says Bethold Kohler, an editor of the Frankfurter Allgemeine Zeitung newspaper. "Nobody could imagine a US president would say such a thing."
Kohler did his bit to prompt a radical rethink, arguing in his prestigious newspaper for Germany to consider acquiring its own nuclear weapons.
But such ideas remain, he believes, more or less "unthinkable and unsayable" for most Germans.
While some are opposed to nuclear weapons in principle, many others spent decades living comfortably under the US and Nato nuclear shield. "No-one expected that we would have to think about it," he says. And few in Germany want to now.
Unique historical experiment?
Germany currently spends only around 1.2% of GDP on defence. "We have a MASSIVE trade deficit with Germany, plus they pay FAR LESS than they should on NATO & military," tweeted President Trump recently. '"Very bad for U.S. This will change."
Germany will resist Trump's calls for huge extra spending, but underfunding has been at times highly embarrassing, such as the revelation that during a Nato exercise in 2014 Bundeswehr tank commanders covered up their lack of machine guns by using broomsticks painted black.
So how far will Berlin go?
Werner Kraetschell, who knows Angela Merkel and her thinking well, says she wants a "strong German army able to take international responsibility". But her difficulty is that "the German people are against the army".
Perhaps the Germans will continue a unique historical experiment, trying to become a growing international power without significant military effort.
For the past still weighs heavily. Whatever happens, there'll be no brash marching into action abroad. Instead, Germany's military will tiptoe warily into a highly uncertain future.