Yacef was the twenty-nine-year-old son of a Casbah baker, seventh out of a family of fourteen, who had begun work for his father at the age of fourteen, a highly self-possessed young man with big, mocking brown eyes, a sensual mouth under a thick black moustache and immense confidence in himself. A keen footballer, he was daring and inventive. Arrested in France, he had managed to talk his way out of Barberousse by persuading the French gaolers of his willingness to act as double agent — to such effect that for some time he was regarded with distrust by his former colleagues. Knowing every inch of the tortuous alleys of the Casbah, so narrow that one can often jump from one roof-top to another, and where one square kilometre housed a teeming populace of 100,000 Muslims, he had persuaded Abane of the advantage of "purging" it of all doubtful elements and turning it into a fortress from which a campaign could be launched. With the aid of skilful masons Yacef had created a whole series of secret passages leading from one house to another, bomb factories, caches and virtually undiscoverable hiding-places concealed behind false walls.

XREF: This connects to histories of urban insurgency and the Battle of Algiers, where dense urban geography enabled covert resistance.

Horne, Alistair, A Savage War of Peace- Alge…, loc. 554