The main principles of the Doctrine of Lapse are that those Indian were not allowed to take any adopted son. If there would be no natural heir the kingdom would pass on to the English. But according to the age-old custom an Indian ruler who had no natural heir could adopt a son.
The British Government did not agree to this Indian custom. It was with the permission of the English that any adopted son could be taken. If any adopted son would be taken without the consent of the English it would be invalid.
Dalhousie by application of the Doctrine of Lapse annexed such territories to the British Empire in India. The 'Doctrine of Lapse' was by far the most important weapon by which Lord Dalhousie implemented his policy of expansionism in India.
Of course it is to be remembered that Lord Dalhousie was only implementing the policy of the court of Directors. The court of Directors had been insisting that no opportunity should be missed to annex territories in India.
However, according to his doctrine 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.