All people should disclose whether they submit to Allah or not. Those who are against us are our enemies and must be fought. That includes people who call themselves Muslims but who don't lead their lives as such - people who drink, who don't pray, who don't fast, who have constantly changing partners and who are unable to recite the Koran.
Although deceit is detestable in all other things, yet in the conduct of war it is laudable and honorable; and a commander who vanquishes an enemy by stratagem is equally praised with one who gains victory by force.