Following the departure of the Khalifah dynasty from Qatar, the country was ruled by a series of transitory sheikhs, the most famous of whom was Raḥmah ibn Jābir al-Jalāhimah, known particularly for his maritime warring with the Khalifah family and their associates.In 1935 Qatar signed a concession agreement with the Iraq Petroleum Company; four years later oil was discovered. Oil was not recovered on a commercial scale, however, until 1949.