Thus the arrival of Nadir Shah, preserved for a short time longer the existence of the Mogul Empire, by the restoration of Mahomed Shah to the imperial dignity; otherwise it must have succumbed to the Maharattas. When Ahmed Shah first invaded India in 1748, the Vizier of the Emperor of Delhi had recourse, as I have already remarked, to the humiliating expedient of calling in the Maharattas. The state of the Mogul Empire in 1756, was much the same as that of Calcutta when it was attacked by Suraj-ud-Dowlah, the Subahdar of Bengal, in June of the same year. No mandate of the Emperor was obeyed: the Nawab of Oude, the actual Vizier of the Empire, had raised the standard of independence: the power of the Maharattas was at its zenith, and that of the Mogul Empire at its lowest ebb. Now the proper country of the Maharattas is the south of India. When Aurungzebe left the Deccan about 1658, he appointed a deputy, who, however, was unable to control the Maharattas. Even Aurungzebe himself when he went in pursuit of Sevajee, the founder of the Maharatta Empire, was often baffled by the wily chief who would suddenly retire into his hills and mountain fastnesses. On the decline of the Delhi power at the death of Aurungzebe, the Maharattas began to extend their operations to the north of the Nerbudda; they gradually threatened all parts of Hindoostan, and even visited Calcutta. At that time, what is called the Maharatta ditch was thrown up to protect the city against these invaders, an ingenious device of the Calcutta factory, and well enough for a body of merchants. The origin of the term "ditchers," as applied to them, is derived from this Maharatta ditch; though it would be as difficult to determine its locality, except on paper, as that of the Black Hole.