Britain would need to fight to gain its empire, and by using the colonies as a resource for soldiers and sailors it grew by an average of 100,000 square miles (260,000 km2) per year between the Battle of Waterloo and the American Civil War.
Serving in the Royal Engineers in the Napoleonic Wars, he was Europe's leading demolitions expert and siege warfare specialist.
He took part in the retreat to Corunna and the Walcheren Expedition, and received a severe wound while gallantly leading a storming party at Flushing.
Though only a captain, his great success led him to act as the commanding royal engineer at Plymouth for two years and was given a special grant.
[1] On 23 November 1841, on promotion to the rank of major-general, he was made an inspector-general of railways,[4] replacing Lieutenant-Colonel Sir Frederic Smith.
During this period of intense activity on the new railway network, he inspected many new lines, criticising the haste in which some were opened to poor engineering standards.
However, he came under criticism[5] for his approval of the North British Railway's line from Edinburgh to Berwick in June 1846;[6] the bridges and earthworks failed to withstand heavy rain in September 1846 and nineteen miles of track were rendered unusable.
[9] In November 1846, the inspectorate was reorganised, with no post for Pasley in the new structure:[10] on vacating this appointment,[4] he was made a K.C.B., and thenceforward was chiefly concerned with the East India Company's military seminary at Addiscombe.
Another son, George Malcolm Pasley (d.1861), served as an officer in the Royal Artillery (South Africa 1849-51 and Indian Mutiny) and as ADC to General Michel in the Turkish Contingent in the Crimean War.