The bombing and shooting rampage in Norway last month has been repeatedly described as the country's worst disaster since the Second World War when Nazi Germany invaded and occupied the country for five years.
For Norwegians, though, their WWII suffering is not just a benchmark. It is also a parallel that foreshadowed the national trauma they're going through today.
As such, what they experienced from 1940-45 and how they dealt with it may well help them overcome this latest national tragedy.
Then, as now, the author of much of their misery was one of their own countrymen, a man whose name passed into English and other languages as a word for ultimate perfidy.
The word: quisling, a traitor who collaborates with his country's enemies to oppress his own people.
The man: Vidkun Quisling, Germany's puppet ruler of Norway.
Quisling distinguished himself from Nazi collaborators in other conquered countries by going to see Adolf Hitler to urge him to invade Norway.
In April 1940, Hitler obliged. But the Norwegians resisted the invaders fiercely.
When the Germans demanded that the Norwegian king, Haakon VII, surrender and appoint Quisling as head of a puppet government, the king refused, even after the Nazis threatened to send all Norwegian men of military age to concentration camps.
His cabinet and the Storting, the Norwegian parliament, supported the king.
Paper clips and saboteurs
Aided by British and French forces, the Norwegians resisted the Germans for two months, longer than any other country invaded by the Nazis, except for the Soviet Union.
Eventually, with their allies withdrawing their forces to try to save France from falling, the Norwegians had to surrender. The king, along with his cabinet and naval forces, managed to escape to form a government in exile in Britain.
Quisling, in the meantime, turned Norway into a copy of Nazi Germany. He transformed it into a one-party fascist state and recruited 6,000 Norwegians to fight alongside the Germans on the Russian front.
But Quisling supporters were only a tiny minority: by most accounts, no more than two per cent of the population. What's more, Norwegians showed their opposition to the occupiers in many ways.
Some did so surreptitiously, by wearing paper clips as a signal that they were all bound together. Others painted King Haakon's "H7" monogram on walls or incorporated it on their clothing or jewelry, practices that could have led to arrest.
More importantly, active resistance continued with widespread sabotage.
Norwegian spotters led to the destruction of German warships by allied bombers. Most notably, saboteurs destroyed a heavy water plant that might have been used by the Germans to build an atomic bomb.
Norwegian resistance compelled the Germans to maintain a large garrison in the country. By the end of the war, the Germans had an army of 372,000 to stand guard over a population of only three million.
When the war ended, Quisling was arrested, put on trial, found guilty of high treason and executed by firing squad.
Vidkun Quisling and Anders Breivik, the perpetrator of Norway's current tragedy, may not seem to have anything in common.
Quisling was the quintessential insider, a high achiever as a student, military officer, diplomat and cabinet minister (before the war) before he turned rogue. In fact, as a young man he was known for being a humanitarian who worked hard trying to save lives in the 1921 Ukrainian famine.
By contrast, until the day of his rampage, Breivik, had no public profile whatsoever and was generally seen as a quiet, courteous nonentity and low achiever.
For all that, though, they were both cut from the same cloth by their obsessive belief in racial purity.
Both, it appears, regarded Norwegians and others like them as superior beings. And had nothing but hate for those they considered inferior.
For Quisling it was Jews. For Breivik, Muslims.
In the end, though, there is something vastly more important that they have in common: It is that the enormity of their crimes brought out the best in their countrymen.
Today's Norwegians reacted to Breivik's depravity, as did those of yesteryear to Quisling's villainy, with quiet dignity, strength of character and a determination to do what is right.
They have reason to be proud of their reactions and deserve our admiration for their devotion to freedom and the long-term constancy of their tight-as-a-paper-clip unity.