A careful campaign of deception ensured Israel was caught off guard when the Palestinian Islamist group Hamas launched its devastating attack, enabling a force using bulldozers, hang gliders and motorbikes to take on the Middle East’s most powerful army.

Saturday’s assault, the worst breach in Israel’s defences since Arab armies waged war in 1973, followed two years of subterfuge by Hamas that involved keeping its military plans under wraps and convincing Israel it did not want a fight.

While Israel was led to believe it was containing a war-weary Hamas by providing economic incentives to Gazan workers, the group’s fighters were being trained and drilled, often in plain sight, a source close to Hamas said.

This source provided many of the details for the account of the attack and its buildup that has been pieced together by Reuters. Three sources within Israel’s security establishment, who like others asked not to be identified, also contributed to this account.