In the wake of the vicious suicide bombing in Manchester, the British government under Prime Minister Theresa May has temporarily suspended an election campaign and done two extraordinary things. It has raised the terrorism threat level to “critical” — something that has happened on only two previous occasions since the 9/11 attacks. It has also deployed the armed forces to guard key public spaces, beginning in London. Military uniforms and guns in the street are not a common or welcome British experience.

The British government’s action is prompted by a fear that more terror attacks are imminent — that is the premise of the critical alert level. Let us all hope the fear is not realized. In the meantime, a critical threat level is a double-edged sword: it gives the government latitude to deploy the military and shift police resources to security threats; it sends a potential deterrent message to any terrorist actors plotting in Britain; it raises the game of the security and intelligence agencies, particularly the police and MI5, which bear the heavy burden of preventing any future attacks through good intelligence work; and it engages the public as the eyes and ears of the government to warn of anything untoward.

But waiting in judgment is the question of overreaction. This is the other edge of the sword. Hindsight will be all, but British politicians with longer memories will recall how former Prime Minister Tony Blair was excoriated for his decision in 2003 to deploy armed forces to Heathrow airport against a threat that failed to materialize.

Whenever a British government reaches for this anti-terror weapon, it does so knowing two things. It knows it has only limited time before the threat level has to come down — the British public does not want to live under such a spectre for long. The government also knows it has only limited public tolerance for guns in the streets. Sooner rather than later, the soldiers have to go back to their barracks. What the critical alert does do is put extraordinary pressure on police and security agencies to identify and roll up any network associated with Salman Abedi, the Manchester suicide bomber.

If networks are the fear, what is the reality? Some might imagine highly trained and skilled sleeper cells deeply embedded in British society, ready to strike on command. That is a fantasy. Closer to reality are concerns about looser associations allowing for support and facilitation — still deeply criminal acts. To date, eight people have been arrested by the Manchester police in connection with the bombing, though British authorities are trying to keep a lid on the details of those arrests. The authorities are simply saying that the arrests are “significant.”

The very first clue that Mr. Abedi did not fit the profile of a “lone wolf” was that his bomb was just too powerful and too sophisticated to be the work of a loner studying bomb-making on the Internet. It would appear he had help; he may have been nothing more than a terrorist “mule.” His travel patterns have also given rise to alarms, with reports surfacing that he had recently visited Libya, where some members of his family are now under arrest, as well as Syria and Germany.

Help is the frightener — help from whom, from where? Two urgent questions face the authorities. What was the extent and nature of any local network supporting Mr. Abedi in his attack? Equally worrying is the extent to which this was a plot not just inspired by an overseas terrorist group, but aided and directed by such a group. All Western intelligence agencies are waiting for signs that groups like the Islamic State and al-Qaeda will shift the centre of gravity of their terror activities from their own home-front fights to their western enemies, as Osama bin Laden once urged. The British have to wonder and fear if they are now at the forefront of such a shift in strategy.

Here in Canada, we are spectators to these extraordinary developments in Britain. The Canadian Security Intelligence Service has a liaison office in London and will have a front-row seat to British efforts to penetrate the plot. It will be CSIS’s job to sniff out any possible Canadian nexus, however unlikely, to the Manchester bombing.

Public Safety Minister Ralph Goodale has indicated that the government knows of no reason to raise our threat level, which currently sits at “medium,” meaning a terrorism act “could occur,” but nothing more.

There are many complex factors that underpin such safety. One is the Canadian Muslim community itself, which has been resistant to any terrorist appeal and has invested in its own efforts to counter the infrequent signs of the rise of radicalization and violence in its midst. The Muslim community, according to a major Environics polling study, Survey of Muslims in Canada 2016, published in April, 2016, holds considerable trust in the Canadian government and Canadian security authorities and seeks a strong relationship with the government in maintaining civic peace. It also wants to see Canada find the right balance between security and rights protections, something that Canadians seem pretty united about, as the government’s public consultations on national security demonstrate.

Worrying about getting the balance right might be seen as a luxury in the aftermath of a terrorist outrage, but it is the biggest question of all.

This article was first published in the Globe and Mail on 25 May 2017.