Religious causes
Francis Bacon said there were five causes for holy war: (he wrote in a Christian context, but the categories would be usable by any faith)
to spread the faith
to retrieve countries that were once Christian, even though there are no Christians left there
to rescue Christians in countries that were once Christian from 'the servitude of the infidels'
recover and purify consecrated places that are presently being 'polluted and profaned'
avenge blasphemous acts, or cruelties and killings of Christians (even if these took place long ago)
Only the first of these causes is completely outside the scope of the conventional idea of a just cause. Some of the other causes, because of the length of time that can pass since the offending act took place are probably not just causes either.
Explanation: