The corps of de Boigne formed part of the army sent under the command of Sindhia's Mahratta generals, Lakwa Dada and Gopal Rao Bhao, to prevent if possible the junction of Ismail Beg with his Rajput allies. But the Moghul soldier of fortune was determined not to yield without a struggle. No sooner did he raise his standard than thousands of disbanded Afghan and Persian horsemen flocked to his headquarters. In March de Boigne left his employer at his favourite cantonment of Mathra, and sending before him a cloud of Mahratta horse, marched upon Ismail Beg with a complete brigade, including fifty pieces of artillery. On the morning of the 10th May they came upon him at a place called Patan, in the rocky country between Ajmir and Gwalior, not many miles from the scene of the former battle at Lalsaut. For three weeks or more nothing was effected, but on the 19th June Ismail announced his intention of attacking the Mahratta lines. De Boigne sent a messenger to say that he would spare him the fatigue of the journey, and advanced to the encounter with all his force on the following morning. The Rajputs had come up; but there was no longer union between them; for the Patel, taking advantage of a temporary soreness felt by the Kachwahas of Jaipur on some trifling provocation, had contrived to secure their inaction before the battle began. Notwithstanding this defection, a large body of infantry still stood firm, but European skill and resolution conquered in the end. Ismail at the head of his Moghul cavaliers repeatedly charged de Boigne's artillery, sabring the gunners at their posts. Between the charges the infantry were thinned by well-directed volleys of grape, and the squares had to be formed with the greatest rapidity as the cavalry of the enemy once more attacked them. De Boigne's squares, however, resisted all attempts throughout the afternoon, and a general advance of the whole line at length took place, before which the enemy gradually broke. De Boigne placing himself at the head of one of his battalions, ordered the others to follow, and precipitated his foot upon the enemy's batteries. The first was carried with the shock; at eight in the evening he was master of the second; the third fell an hour later; the Moghuls' resistance was completely overpowered, and their leader was chased into the city of Jaipur. Ismail also lost in this engagement one hundred guns, fifty elephants, two hundred stand of colours and all his baggage; and on the following day a large portion of his army, amounting to seven battalions of foot and ten thousand irregular troops, went over to the victors. On this, as on many other occasions, the Mahratta cause was jeopardised by jealousies; Holkar holding aloof during the action, which would have begun earlier, and in all probability proved more decisive and with less loss, had he given due co-operation. There is a modest account of this action from de Boigne's pen in the Calcutta Gazette for 22nd July, 1790.