'Lee-ve it aht, Rodney'

Burnished Rows of Steel, Chapter 9, Part 3:

Grant’s chief topographical officer, Captain Thomas Jefferson Lee, who despite his relatively low rank, was among Grant’s most valuable staff officers on the Saint Lawrence. Lee was one of those individuals – not unlike Wolseley – who would strike an observer as improbably well-suited for the task at hand.Born to American parents in 1808 in Bordeaux, Lee was fluent in French. Appointed to West Point in 1826, he graduated in 1830 and served in the artillery, engineers, and topographical engineers over the course of a 30-year-long career, including duty in Europe, service as an aide to Winfield Scott, and, most notably, with the international boundary surveys on the northern frontier in the 1840s and of the Great Lakes in the 1850s. Lee retired in 1855, but when the Anglo-American crisis came to a boil in the winter of 1861-62, he offered his services. Lee returned to the colors and had played significant roles in the crossing of the Niagara, at Limestone Ridge, and the siege of Kingston; he was ably assisted by his deputy, Lt. George W. Rose, class of 1852, another “rallier” – a Detroit merchant, Rose had served with Lee on the Survey of Northwestern Lakes and knew Upper and Lower Canada as well as any British officer. Both men were examples of the resources the Anglo-American conflict had brought into the field for the Americans, resources which in a solely civil conflict might never have appeared

Notice that we are not told that Lee never saw combat, as we would be if Lee were British. TFsmith presumably thought that 'service as an aide to Winfield Scott' would con his readers into thinking that service came during the Mexican-American War. Or perhaps he really doesn't understand what aides do. However, take particular notice of that last sentence:

Both men were examples of the resources the Anglo-American conflict had brought into the field for the Americans, resources which in a solely civil conflict might never have appeared 

Thomas Jefferson Lee's biography explains that he was 'employed on the Coast Survey, 1861‑62' and 'by the Bureau of Topographical Engineers, 1862‑63'. His obituary specifies further that his service in the latter capacity was 'in connection with the defences of Washington'.

In BROS, some of the country's few trained military officers are drafted out of the Coast Survey and the Topographical Engineers, and into staff roles with armies in the field. However, this transfer of personnel has no effect on the Union's ability to defend its coastlines or its northern border with Canada, despite this task requiring the construction of vast numbers of submarine obstacles, earthen land batteries, and masonry forts which the country had been unable to complete in peacetime. Nor does Lee's absence from the Washington defences matter, as the Confederates sit and do nothing while the Union transfer vast numbers of troops north - how very fortunate.

Once again, that hand behind the Union's back turns out to have been in use after all.