By December 1940 the plan had been extended. While the first British striking force headed for Dublin, the British 61st Division, in a separate operation, would move across the border into County Donegal and secure the Treaty port of Lough Swilly for the Royal Navy, providing the British Government with a third of the naval defence requirements that they had been requesting from de Valera for more than a year. The British Troops in Northern Ireland (BTNI) war diary of the time lists 278 Irish troops at Lough Swilly and only 976 Irish troops in the rest of Donegal.