By Jonathan Marcus
Diplomatic correspondent, BBC News
Things that do not happen are sometimes as vital as actual events to understand what is really going on.
Israel has admitted its jets attacked a Syrian target on September 6
In one of the fictional detective Sherlock Holmes' most famous cases, the crime was solved by a vital clue - the dog that did not bark in the night.
And in the real-life drama of the Israeli Air Force's raid on a target in Syria last month, there are two particular "dogs" that have not barked.
For all of its protests the Syrian government has done as little as possible to play up the incident.
There have been no trips for journalists to visit the bomb craters, no orchestrated campaign to condemn Israel for what in any other circumstances would be seen as an unwarranted act of aggression.
In the United States the diplomatic effort to engage North Korea and roll back its nuclear programme has remained on track, despite all the suggestions that what the Israelis actually hit was a North Korean-supplied nuclear research facility in Syria.
Wall of silence
Indeed there are indications that North Korean scientists and technicians may have been killed or wounded in the attack.
North Korea's involvement in spreading nuclear technology and know-how might, in most circumstances, be expected to draw strong condemnation from Washington.
More than four weeks after the air strike during the early hours of 6 September, hard facts about the operation remain scarce.
There are indications that North Korean scientists may have been killed in the attack
In Israel the episode has been surrounded by an unusually high degree of military censorship.
Pundits and military experts who profess to know many of the details of the operation are saying nothing.
The leader of Israel's conservative Likud opposition party, Binyamin Netanyahu, was the first to break the wall of silence.
His apparent confirmation of an Israeli operation against a Syrian target drew considerable criticism from his political opponents.
At the end of last month Syrian Vice-President Farouk Ashara said the target attacked by the warplanes was "an academic research centre for the study of arid soil".
Subsequently Syrian President Basher al-Assad had a different story, telling the BBC that the target was "an unused military building".
This acknowledgement that an attack really did take place seems to have opened the way for a partial lifting of the censorship restrictions in Israel, with confirmation of the raid but still no details about the target, the nature of the forces involved, or any assessment of its success.
Much of the reporting of this story has come through unattributed leaks in the US press.
There have been suggestions that Israel delayed the operation at Washington's request and reports that Israel sent soil samples from the location to the US for analysis, as proof of their contention of a nuclear connection.
These reports amplify earlier suggestions that elite Israeli troops were present on the ground as part of the operation.
Most recently, reports in The New York Times speak of divisions within the Bush administration, with contrasting views as to the significance of the intelligence the Israelis had provided.
The administration, says the report, was divided along predictable fault lines with Vice-President Dick Cheney and "conservative hawks" in the Administration believing that the Israeli intelligence was credible and should prompt a reassessment of Washington's opening to North Korea.
US Secretary of State Condoleezza Rice and Defence Secretary Robert Gates were said to be much more cautious.
Deterrent capability restored
Either way the operation clearly went ahead.
That it did so at a time of escalating Israeli-Syrian tension is indicative in itself.
Either the Israelis believed that the stakes were so high and the intelligence so strong that the risks were worth it.
Or alternatively they may have taken the view that such an operation was the best way of reminding President Assad that Israel's military reach had not been stunted by its failures in southern Lebanon last year.
Some days after the operation, Israeli Defence Forces Intelligence chief General Amos Yadlin made a statement to the effect that Israel's deterrent capability had been restored.
Or maybe he did not, because an official denial of his comments was subsequently released. Did he bark or maybe should he have remained silent?