Ahmed Shah had accompanied Nadir Shah to Delhi in 1739, and had seen the weakness of the ruler there. To pay for the maintenance of the army, he had to conquer new lands. His own country had no resources at all, compared with the vast wealth of India. Apart from that, he wished to enhance his own reputation in Afghanistan by capturing a neighboring country. He attacked Peshawar and drove out its Mughal governor Nasir Khan in October 1747. Just about then, he received an invitation from Shah Nawaz Khan to invade and annex the provinces of Multan, Kashmir and Lahore, saying that he would co-operate fully in this campaign in return for his own confirmation as governor of Lahore.
In December 1747, Ahmed Shah set out from Peshawar, and arrived at the Indus river-crossing at Attock. From there, he sent his messenger to Lahore, but the man was given a rough reception by Shah Nawaz, who was then a different man. He had been won over by the Delhi minister with an offer of confirmation in his appointment of Governor of Lahore. Thus, when Ahmed Shah reached the bank of the Ravi on 8th January, 1748, the Lahore army of 70,000 prepared to oppose the invader. The Pathans crossed over on the 10th of January and the battle was joined on the 11th. Ahmed Shah had only 30,000 horsemen, and no artillery. But during the battle, a force of 5,000 Pathans of Qasoor under Jamal Khan defected to his side, and he was able to crush the poorly trained forces of Lahore. Shah Nawaz fled to Delhi, and Adina Beg was equally fast in running away to the Jalandhar area.
Ahmed Shah entered the city on the 12th January 1748, and set free Moman Khan and Lakhpat Rai. He then ordered a general massacre. Towards evening, the prominent leaders of the city including Moman Khan, Lakhpat Rai and Surat Singh collected a sum of three million rupees and offered it as expenses to Abdali, requesting him to halt the looting and slaughter. Ahmed Shah appointed Jamal Khan of Qasoor Governor of Lahore, and Lakhpat Rai his minister, and restoring law and order around the town by February 18, he set out towards Delhi.
Meanwhile Qamar-ud-din Khan collected an army of 200,000 and marched towards Sirhind which was reached on 25th february. Here he found that the Rohela commander of Sirhind, Mohammed Khan had fled into the hills on hearing about the advance of Ahmed Shah. Qamar-ud-din left his baggage and his begums under the protection of 1,000 men at Sirhind, and advanced towards Machhiwara. Ahmed Shah crossed the river Satluj at Phillaur on the 1st March at night, and reached Sirhind the next day to Jind it almost undefended. On hearing about the capture of his beghams, Qamar-ud-din hastened back, and on the 11th March, 1748, the two armies clashed in battle at Manudur. Qamar-ud-Din was killed in one of a series of skirmishes that went on for some days. His son Muin-ul-Mulk (Mir Manu for short) took over the lead, and he made such a furious charge that Abdali's men gave way, and fled. By 17th March, Abdali was crossing the Satluj and heading towards Lahore, with Mir Manu following him, but at a safe distance behind.
This train of events seemed to have been specially designed by Providence for the benefit of the Sikhs, who lost no time in making the most of their good fortune. Yahya Khan had tried his best to annihilate them during his short stay of 15 months as Governor of Lahore. But after October 1746, his energies were diverted to his own welfare on account of the activities of Shah Nawaz and Adina Beg. Shah Nawaz Khan was too preoccupied with the confirmation of his command over the Punjab by the Minister at Delhi, to give the Sikhs much trouble. Then when the Afghan threat loomed in January 1748, he had called up Adina Beg from Jalandhar, leaving the Sikhs completely free to raid and occupy large tracts of land in both the Jalandhar and the Bari Doabs. During the two months that Abdali spent marching down from Lahore to the battle at Manupur, the Sikhs were busy taking control over the countryside, and chastising those choudhries who had informed on them. Rama Randhawa of Ghanayan, Harbhagat of Jandiala, Dharamdas of Jodh Nagar, Sanmukh Rai of Wadali, the Khatris of Patti, and the Ranghars of Sheikhupura were amongst those that were put to the sword. Village headmen would inform on Sikhs in future only at their own peril.
Whilst Abdali was engaged at Manupur, Jassa Singh's band swooped upon Amritsar, which was then under the charge of one Salabat Khan. This Commander was slain in the fight and his troops fled, leaving the city and its holy tank in the hands of the Sikhs. The partly earth-filled tank was cleaned up, and the masses were once more able to take their ablutions there.
When Abdali began his retreat from Manupur in March 1748, the Sikh bands under Jassa Singh, Charhat Singh and Karora Singh gave him a taste of the same guerilla raids that had been applied on Nadir Shah. Mir Manu was coming too far behind to bother Ahmed Shah. The Sikhs would swoop down on Abdali's camp at night and make away with baggage and horses. They continued with this harassment till he reached the hanks of the Chenab. Here they stopped because Vaisakhi day that year fell on the 29th March, and they wished to celebrate it at Amritsar.
This was the first Vaisakhi they had celebrated after many years, in complete Freedom, and it also marked a new phase in the organization of the Dal Khalsa. The holocaust of 1746 had shown up the weakness of small groups or jathas fighting under separate leaders.