ATHENS — For decades, a large bomb sat under a gas station in a densely crowded neighborhood near the heart of Thessaloniki, Greece’s second-largest city. Last Sunday, the authorities evacuated some 72,000 residents from the area so a military explosives disposal crew could defuse the 550-pound bomb and take it away. It was reported to have been dropped in an Allied raid in World War II, when Greece was under German occupation and members of Thessaloniki’s ancient and flourishing Jewish community were being murdered in camps in occupied Poland.

In Greece, the wounds of history are never far from the surface. And this small country on Europe’s periphery sits squarely on the fault lines of the many difficulties that face Western democracies today. For seven years now, Greece and its creditors have failed to defuse the European Union’s first great crisis since the euro was adopted, despite the biggest bailout of a debtor in history. Donald J. Trump’s election, the Brexit vote and the inexorable rise of anger and aggression in the politics of many nations further undermine the European Union and threaten the achievements and promise of liberal democracy itself.

The last time a political system was under such stress was in 1989, when the collapse of the Berlin Wall revealed the bankruptcy of the Communist system. What liberal democracy and the open economy face today is not the failure of their promise of stability and prosperity for ever greater numbers of people — it is not the system that is exhausted but those who should protect it from its failings and from its enemies. Nowhere is the array of problems and the lack of leadership more evident than in the case of Greece.

Even as the Thessaloniki bomb was being dismantled, Greek officials and the representatives of foreign creditors were stuck in the latest of a seemingly endless series of talks aimed at releasing bailout funds in return for Greece carrying out more economic reforms and imposing further austerity. Failure to reach a deal could mean Greece defaulting in July on debt payments to the European Central Bank, other creditors and investors. This could prompt the country’s exit from the eurozone, something that previous talks were believed to have settled. But the Greek crisis is even more significant: It reveals the dangerous rifts among major players and the lack of leadership and vision at the European Union level.