Who combined the separate kingdoms of Jammu, Kashmir and Ladakh into one empire?

On 16^th March 1846, the 'Treaty of Amritsar' was signed between the British Government and the ruler of Jammu 'Raja Gulab Singh'. Maharaja Gulab Singh became the ruler of Kashmir, but according to the treaty he was a vassal of the British and had to pay an annual tribute in acknowledgment of their supremacy. Maharaja Gulab Singh had already annexed Ladakh region. Thus, a new state with three distinct regions, viz, Jammu, Kashmir and Ladakh was formed under the rule of Maharaja Gulab Singh.