The Three Investments:
The three instruments by the application of which Lord Dalhousie expanded the British Empire to its greatest extent were : (1) War of annexation (2) Doctrine of Lapse and (3) Annexation on the ground of misgovernment..
The Most Important one:
The ‘Doctrine of Lapse’ was by far the most important weapon by which Lord Dalhousie implement his policy of expansionism.
The Doctrine of Lapse:
According to the Doctrine of Lapse when the ruler of a native state died without a natural heir, his state was not to pass on to an adopted heir. That is to say, Lord Dalhousie deprived the native rulers of their right to adopt an heir as sanctioned by the age-old tradition of the country.
Through the application of the Doctrine of Lapse Satara, Jaitpur, Sambalpur, etc. were annexed to the British Empire when their rulers died without a natural heir. Thus the Doctrine of Lapse brought about tremendous success in the expansion of the British dominion in India.