The Telegram & Gazette of Worcester (Mass.), Oct. 23:

The conflict between Western allies and the Islamic State appears to have spread this week beyond the battlegrounds of Syria and northern Iraq, to an unlikely spot ”“ Canada’s capital, Ottawa.

The fatal shooting of a Canadian soldier at that nation’s National War Monument, and a subsequent gun battle inside the nearby Parliament building that left a gunman dead, are stark reminders of the fluid and unpredictable nature of the conflict.

The violence comes just two days after another suspect, said to have jihadist sympathies, ran over two Canadian soldiers, killing one, in an act described by a top Canadian official as “clearly linked to terrorist ideology.”

Canada earlier this month pledged air support for strikes against Islamic State militants, and like the U.S., Britain, and other nations, has seen some of its citizens traveling to the Middle East to fight with the militants or expressing support for them.

Canadian security forces and authorities were working yesterday to determine whether other suspects might still be at large or involved in carrying out the attacks on Parliament Hill.

But this is already clear: All nations must remain vigilant against the threats of terrorist ideology. Whether terrorists act individually, conspire to carry out small-scale attacks, or attempt to lend material support to Islamic State, they must be detected, apprehended, deterred, and defeated.