She once strode across the European stage like a colossus.
German Chancellor Angela Merkel used to be the de facto leader of mainland Europe, the guardian of the continent's liberal ideals, champion of European unity and standard bearer of German economic dominance and prowess.
This week's barbaric act of terror on the streets of Berlin, however, served as a stark reminder of the limits of Merkel's power, the inherent risks of her open borders approach to the refugee crisis and the extraordinary failures of German federal authorities in the face of the rising Islamist threat.
The chief suspect in the brutal attack on a Christmas market at the heart of Berlin is a Tunisian asylum-seeker, Anis Amri, who had already been the subject of an earlier German terror investigation but had been released instead of being deported, despite being in touch with radical Islamists, including a recruitment network for ISIS operating in Germany, German security officials told CNN.
Merkel's naive liberalism?
The brutal atrocity has shone a huge spotlight on Merkel's highly controversial decision to welcome nearly 1 million migrants into Germany since the start of 2015 as well as her government's lax deportation policies and striking failure to act aggressively against Islamist militants.
Merkel's popularity had already fallen to a five-year low before this latest terror attack, with an approval rating in September of just 45%.
It will likely plunge even further in the coming weeks as public outrage swells, with discontent in the ranks of Merkel's Christian Democratic Union and its Christian Social Union partners certain to grow.
Merkel will represent her party in the German federal elections next fall, but if she is returned to office for a fourth time, it may be as a significantly diminished figure.
The Berlin attack is sending shock waves across an increasingly nervous Europe, and will intensify the criticism from other European leaders, especially in Eastern and Central Europe, of Merkel's migrant policy, which has left the rest of the continent in a far more vulnerable position.
Merkel's stance on the refugee crisis was strongly rejected by the rising powers in the east, including Poland and Hungary.
German power within the European Union was once formidable.
Today, it is increasingly challenged and rejected.
Clinging to European project
Unlike her British counterpart, Theresa May, Merkel looks remarkably out of touch with the winds of change sweeping through Europe, ignoring the growing calls for greater sovereignty and control over national borders.
She clings to a withering European project, ardently defending the European single currency while extolling the principle of freedom of movement across Europe in the face of mounting unease and fear at home and abroad.
She is also seemingly unwilling to confront the sheer scale of the Islamist terror threat to Europe, and to acknowledge the fact that her own refugee policies have greatly exacerbated the dangers.
Incredibly, Merkel has elevated a naive liberal humanitarianism over the national security of her own country.
The deep-seated problems facing Merkel are part of a broader long-term decline of German power.
In the coming decades, Germany will wrestle with a dramatically falling population and reduced economic competitiveness.
Great Britain is already on course to be Europe's largest economy by 2030, according to the Centre for Economic and Business Research, and will overtake Germany as the most populous nation in Western Europe by the middle of the century.
Merkel's heyday in the first decade of this century will likely be remembered as the highpoint of modern post-war Germany.
But the challenges faced by Germany today are significantly greater than they were just a few years ago.
Germany's Chancellor must act decisively in the face of the mounting terror threat, and regain control of her own country's borders.
Europe is dramatically changing, and Merkel must be prepared to adapt with it.
Nile Gardiner is the director of the Margaret Thatcher Center for Freedom at the Heritage Foundation and a former aide to the late British Prime Minister. Opinions in this article belong to the author.