KATTANKUDY, Sri Lanka — When the Wahhabis came, with their austere ideology and abundant coffers, the town of Kattankudy yielded fertile ground.

In this part of Sri Lanka, faith was often the sole sustaining force during the civil war that raged for nearly three decades. Wahhabism — a hard-line strain of Islam blamed for breeding militancy — proposed a direct path to God, albeit one that aimed to return the religion to the time of the Prophet Muhammad.

It was here in Kattankudy’s warren of homes decorated with delicate swirls of Arabic calligraphy that Zaharan Hashim, the man accused of masterminding the Easter Sunday attacks in Sri Lanka, grew up. And it was here that he preached his ideology, calling for the killing of nonbelievers in Islam and even other Muslims.