It is easy to think that war-fighting is deteriorating into barbarism. The Islamic State's campaign of terror, Boko Haram's sexual violence and use of child bombers, the razing of Aleppo are all playing out in horrific immediacy on social media.

Now the largest-ever survey on attitudes to war reveals a tougher, more cynical public view on how fighting is done, including the statistic that nearly one quarter of Australians think torturing enemy soldiers is justifiable.

The survey of 17,000 people in 16 countries, published by the International Committee of the Red Cross on Monday, found that while most people still believe war should have rules, faith in the Geneva Convention is fading and there is growing acceptance of torture and civilian casualties.

It is prompting the Red Cross, the respected organisation that works in the world's most dangerous places, to call for a renewed effort to promote the virtues of rules in warfare.