(CNN)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. December'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.
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%.