No-one should be surprised that a Christmas market was attacked or even the way the attack was carried out.
But the challenges in preventing such low-tech attacks are complex. A decade ago those working with al-Qaeda tended to plan more complex attacks involving explosives. This often required international travel and training as well as communication and such plots took time to develop.
This all provided potential opportunities for intelligence agencies to learn about the plans and interdict them.
But if an individual is inspired by so-called Islamic State but not in touch with them and acts either alone or in a small cell, then it can be harder to spot them. By the time they hijack a lorry just before an attack, the worst case is that it is more of a case of protecting possible sites rather than spotting them.
There may be questions though as to whether enough was done in Berlin given that this threat was known about.
The US state department issued a warning in late November telling American citizens to exercise caution at "holiday festivals, events and outdoor markets".
Increased security was put in place at some Christmas markets – such as the more famous one at Strasbourg with checks on people and restrictions on vehicle movements.
But one risk is that if all markets are not secured to the same standard, it might simply divert an attacker to a less well defended target.
German officials have sought to defend their preparations, especially since there do not appear to have been obstacles capable of stopping a lorry in Berlin.