Terror attacks in Paris underline the importance of genuine cooperation in the fight against terrorism
The atrocities in Paris were bound to bring the world's leaders together in a pledge of solidarity against Islamic State.
Inevitably, the events overshadowed the Group of 20 summit in Turkey, turning discussion to stepping up the fight against Muslim extremists; more is likely at the Asia-Pacific Economic Cooperation forum in Manila in the coming days.
But as much as there is agreement on what needs to be done, there is a daunting gap in deciding how it is to be achieved. Without a coordinated strategy with shared objectives, there is no hope of ending the spreading slaughter.
Preventing attacks is difficult, even with improved intelligence and security.
The mix of home-grown extremists directed by a well-funded group using sophisticated tactics against unsuspecting citizens is hard to detect.
Islamic State has taken its fight global, Paris being the latest in a string of a dozen attacks that it has claimed over the past year, including Thursday's blasts in Beirut that killed at least 41 and the bombing last month over Sinai of a Russian plane carrying 224 people.
French President Francois Hollande and his US counterpart, Barack Obama, have pledged to destroy Islamic State, and air strikes on its positions in Syria and Iraq have been stepped up.
READ MORE: France strikes back: Warplanes pound Islamic State targets in Syria days after Paris terror attacks
G20 leaders have promised better intelligence sharing, tighter border controls and a crackdown on terrorist financing. Obama and Russian President Vladimir Putin set aside chilly relations to agree that the UN would mediate talks between the Syrian regime of Bashar al-Assad and opposition.
The civil war in Syria and weak governance in Iraq allowed the rise of Islamic State.
Such rhetoric falsely gives the impression of a common strategy. The US-led coalition and Russia have different agendas, with Obama seeking Assad's removal and Putin backing his staying in power.
The coalition is as disjointed, with Turkey seemingly more intent on fighting Kurdish rivals, Britain focused on Iraq, Arab members Saudi Arabia, Jordan and Qatar distracted by Iranian-backed separatists in Yemen, and Canada pulling out.
Only the Kurds and Iraq have ground forces and their abilities will remain limited unless they are joined by Western soldiers - something voters would not accept.
A joint strategy that is more aggressive is only a fraction of the solution. Governments have to placate young Muslims who feel marginalised.
But stopping Islamic State's expansion, destruction and hatred ultimately lies in ending the instability in Syria and Iraq. That will happen only if governments genuinely work together.