Shah Alam II was the Mughal Emperor during the first invasion of Ahmad Shah Abdali. Let's examine the details of this invasion and how it greatly weakened the Mughal Empire.

Ahmad Shah Abdali's Invasion
During the mid-18th century, the Mughal Empire was already facing internal conflicts and struggling to maintain its control over the Indian subcontinent. It was during this time that Ahmad Shah Abdali, the founder of the Durrani Empire (Afghanistan), embarked on a series of invasions into India.

Shah Alam II's Reign
Shah Alam II became the Mughal Emperor in 1759 after the death of his father, Alamgir II. He ascended the throne at a time when the Mughal Empire was already in decline, with regional powers like the Marathas and the Sikhs exerting their influence.

The First Invasion
Ahmad Shah Abdali's first invasion of India took place in 1759, during the reign of Shah Alam II. He led a massive army consisting of Afghan and Rohilla soldiers and aimed to plunder the wealthy cities of northern India, particularly Delhi. The invasion resulted in the Battle of Delhi, which took place in 1760.

Consequences of the Invasion
The invasion led by Ahmad Shah Abdali had several significant consequences, which greatly weakened the Mughal Empire:

1. Loss of Territory: As a result of the invasion, the Mughal Empire lost control over significant territories in northern India. Abdali's forces captured Delhi and plundered the city, causing immense destruction.

2. Economic Drain: The invasion resulted in a massive economic drain on the Mughal Empire. The wealth of Delhi was looted, and the imperial treasury was depleted. This weakened the empire's financial resources and ability to govern effectively.

3. Political Instability: The invasion further destabilized the already fragmented political landscape of the Mughal Empire. Regional powers like the Marathas and the Sikhs capitalized on this weakness and expanded their influence, diminishing the authority of the Mughal Emperor.

4. Weakening of Central Authority: The invasion highlighted the Mughal Empire's inability to defend itself against external threats. This undermined the central authority of the emperor and further weakened the empire's hold over its provinces.

5. Rise of Regional Powers: The invasion of Ahmad Shah Abdali paved the way for the rise of regional powers such as the Marathas, who emerged as significant players in the power dynamics of the Indian subcontinent.

In conclusion, Ahmad Shah Abdali's invasion during the reign of Shah Alam II greatly weakened the Mughal Empire. It resulted in the loss of territory, economic drain, political instability, weakening of central authority, and the rise of regional powers. These factors contributed to the continued decline of the Mughal Empire and its eventual downfall.