First, the Union had to both defend against invasion, and invade, and occupy as long as the insurrection continued, a big job. Like the dog that walked on his hind legs, the wonder is not that it did it ill, but that it did it at all.
Second, there was no war on women and children, except that which the rebels made by occupation of various cities, making the cities an object of battle. While the pretended Army of Northern Virginia fought outside cities, the US Army was content to kill them there. Once the outmatched southern forces retreated to cities like Vicksburg, Atlanta, Richmond, the war followed.
Invasion? Are you serious? Uh, I believe almost all of the War of Northern Agression was fought in Southern soil.
there was no war on women and children
Such was General Sherman's stated aim! As a resident of the state of Georgia, I can assure you that there was, indeed, a very harsh war waged on women and children, and have read hundreds of letters of the era detailing the devastation wrought on farms and families, of Union soldiers picking clean the fields and barns and livestock everywhere they went like a plague of locusts, of the women who hid loaves of bead in baby carriages just to survive, or to attemot to survive. As for cities, the South was a largely rural society, but of course the cities were defended. People lived there! Homes burned down in cities are still homes. Other than Savannah, most cities were simply torched. Shall I bring up the slave women of Columbia whom the Union soldiers infamously raped? And the economic devastation on the entire population of the South, yes, women and children included, was to last for generations. Lincoln's war on his own people is one of the greeat travesties in the history of mankind.