The early morning terrorist attacks at the main Brussels airport in Zaventem and at a crowded metro station shocked the whole world for their barbarity, their indiscriminate nature and the large number of innocent civilian casualties.

The death toll of that bloody morning came to 34; hundreds were injured.

Although Belgium was on high alert following similar multiple terrorist attacks on several Paris locations in mid-November 2015, the blow was severe.

Police in these two countries were aware of links between terrorist cells operating in their capitals.

One of the Paris murderers, Salah Abdusalam, who had been on the run and hunted by the Belgian police since the November Paris attacks, was arrested just a few days before the Brussels attacks.

We know he was intricately involved in the preparations for the Brussels murders, set for the Easter holiday, but the attacks were brought forward following his arrest.

Much has already been uncovered about the two crimes as well as the ties that linked the cells together. And yet, the fear of what possibly remains hidden keeps the intelligence communities in both countries, indeed all over Europe, on maximum alert.

Most startling is the fact that the Brussels murderers were all known to the police; all have criminal records.

One of them, Brahim El Bakraoui, was returned from Turkey following his capture on the Syrian-Turkish border with vital information, including that he was a “foreign terrorist fighter”, passed to the Belgian authorities.

The bombs that were used in Brussels, as in Paris before, were made in a rented Brussels apartment from which suspicious, very strong, chemical odours were constantly felt by people nearby.

The Bakraoui brothers, Brahim and Khalid, who blew themselves up at the airport and the metro station on March 22, had been known for years to the Belgian police as common criminals. Both served long jail sentences for armed robbery and carjacking.

The revelation of such vital information about the criminals makes one wonder why they were left free to prepare for their heinous mass murders, particularly at a time when the Belgian authorities were on maximum alert.

Well, the one lesson to be learned as a result is that no amount of police precaution, intelligence gathering and monitoring can prevent all terrorist attacks.

They can prevent some, but the few that can often escape police notice are devastating enough to create revulsion and horror.

The stunning reality is that security measures, no matter how advanced, are often countered by criminals, creating a vicious and endless spiral of action and counter action.

It is hard to imagine security precautions that can prevent a suicide terrorist who plans to blow himself or herself up near a crowd, wherever that may be.

Previously, it was relatively possible to protect people in closed areas — cinemas, restaurants, shopping malls, schools, offices, hotels and the like — by searching people at the entrance. That also applied to airports when the terrorists’ targets included hijacking or blowing up passenger planes in the sky.

What happened in Zaventem was a different tactic altogether. The attackers detonated their bags full of explosives and blew themselves up in the crowded departure hall well before the baggage is usually checked in and inspected.

Many rushed to ask why those terrorists who drove their trolleys carrying bomb-loaded luggage into the departure hall were not searched.

The answer is simple. If passengers were to be searched at any check point, no matter how far from the airport building, the search will form a crowd and that crowd would be for the terrorist purposes as good as the departure hall.

That will not solve the problem. A terrorist whose goal is to kill himself and others with him could blow himself up in any gathering in the street. Only searching every individual anywhere can prevent that, but that is obviously impossible.

As terrorist are targeting all of us, nations and peoples, indiscriminately and with utmost savagery, and as all means of addressing the symptoms have failed, quite miserably, we need to look for other options.

We need to address the root causes as well.

In various forms and through different means, the war on terror has been ongoing for decades. However, the global war on terror that was initiated in the aftermath of the September 11 terrorist attacks on targets in the US has created more terror than it actually destroyed.

Daesh is one such creation. The terrorist group, which proved to be most dangerous, most vicious, most capable and clearly most appealing to a variety of people, has been left unchecked to grow deep roots and to control vast territory.

Daesh is the incubator of the kind of terror hitting all over the world. Its recruits include highly skilled military personnel from the disbanded Iraqi army who joined with their expertise and sophisticated military gear.

The group also includes naïve and foolish young adventurers from European countries, as well as from the region, mercenaries, thugs, gangsters like the Belgian terrorists, religious zealots, as well as high-level political opportunists.

Sadly, the political opportunism of some states that tried to exploit Daesh in their disputes with others helped create the monster that turned against its creators.

Daesh was repeatedly put on the top of the priority list of the allied powers, or so we were told, but it is still potent and fighting fiercely in Syria and Iraq, and organises terrible terrorist attacks worldwide.

It is time for adequate political will to collectively mobilise to crush Daesh.

Next should come the long-term remedial measures that need to clear the ideology of death and indiscriminate evil. That is going to be long term and tough. But any further procrastination means more terrorist attacks.