Pretty accurate.
Grant is usually held up as some great conqueror, but the entirety of the Overland Campaign sees Lee constantly getting the better of him. Case in point is the Wilderness, where he outnumbered Lee around 2-1 but Lee manages to collapse both of his flanks and ends up forcing Grant to abandon the battlefield because he can't push Lee back. You than get the Courthouse fight, and then after that while maneuvering to the North Anna we see Grant try to be slick by using Hancock's Corps as bait; not only does Lee avoid that trap, he still manages to threaten Hancock to the extent that Grant is forced to give up his plan and attempt to rush to save Hancock. What makes it funnier is Lee had to cross something like three different fords, but still moved faster than Grant. You then get the North Anna action where Lee is able to once again achieve a strong defensive position that forces Grant to divide his army in three different portions, with two over the North Anna itself with only route of escape each, and to the extent that they can't support each other. Lee has interior lines and his flanks are covered by swamps, so he can concentrate on either side. If it wasn't for Lee catching a bout of sickness, Grant would've lost damn near half his army that engagement.
I could go on, but the point is well made. Grant's luck was that by 1864 the South, given its smaller population, was having a harder time sustaining casualties than it could previously. Lee's Army was more worn out than it had been in previous times, and Grant further had the extreme luck of being able to risk taking excessive losses unlike earlier Northern commanders combined with a situation conducive to such; the danger of foreign intervention had receded enough. As it was, Lincoln had to expend serious political capital given widespread outrage at Grant and was decisively helped by Atlanta falling in this regard. As it was, Grant's loss meant we ended up seeing the Siege Warfare around Richmond because he lacked the ability to take the city.
Also, for the record, no, Grant did not invent Trench Warfare nor did he present any innovations in warfare. Trench warfare has been around since at least Medieval times and Grant's maneuverings were no real achievement.
