> How technology can stop the war?
Better technology can help countries to be more productive and less dependent on other countries. This would reduce tensions between countries and consequently reduce armed conflicts.
> Or decrease tensions between religion groups?
Tension between groups can be reduced by making people more aware about how people in the other group are really. For example, a Christian can change his mind about Muslims after spending time talking with a Muslim. With technology you can help people in different groups to understand better people in the other group.
Of course these are speculative answers, and technology has been proven to be highly unpredictable (people predicting that in 2020 there would be flying cars) so I know my predictions are probably false. But they are useful to understand how technology can help. On the other hand, history shows us that technology has helped consistently the (read the article posted here for an extensive list of example).