Lincoln understood that the civil war was not a war for territory. It was about breaking the will of the Confederacy to fight. This required focused tactics that maximized destruction of war materials -- include civilian war capacity -- and direct assault on the army for the purpose of either capturing or killing (or driving to dessertion) confederate soldiers. "It is the confederate army, not Richmond, which is your objective" Lincoln wrote to Hooker, urging him to persue the enemy north rather than to hold the Army of the Potomac ready to march on the Confederate capital. Similarly, Lincoln was bitterly disappointed when Meade allowed the Confederate army to retreat south of the Potomac after Gettysburgh, rather than crushing them in a final assault.
Grant and Sherman took this to heart. They compelled the southern surrender by rutheless destruction of civilian property. Sherman's famous March to the Sea began with the total destruction of Atlanta and cut a swath of devestation through Georgia that became a byword for destructive power. Grant engaged in similar tactics, targeting Confederate commercial centers and destroying captured rebel property.
The allies took a similar approach in WWII. They required complete and unconditional surrender. The conventional wisdom was that by allowing Germany to surrender in WWI with its industry and warmaking capacity intact, the allies had created the environment for Hitler's rise and recreation of the Axis war machine. It wasn't enough for the access powers to lose battles, they needed to be beaten, their will to fight utterly crushed, and no possible excuses or explanations that would become the mythology for another war government to arise.
The reaction to the unprecedented destruction and misery of WWII was the evolution of the modern rules of war, which seek to minimize casualties and/or destruction of civilian property. If we are to have war, let us at least try to make it as painless as possible. Indeed, we have gone beyond previous treaties that merely aspired to this to a claim of internatonal law that certain military actions against civilians constitute war crimes. This generation would (and many do) condemn the firebombing of Dresden and of Tokyo as war crimes and crimes against humanity.
Unsurprisingly, the issue raises itself in the current conflict in Gaza. It is not that the conflict of war crimes is new. Indeed, it was invented in the modern era in the aftermath of the civil war with the trial and subsequent hanging of the former commandant of Andersonville prison. But the current doctrine that the deliberate bombing of civilian targets for the purpose of breaking the will of the enemy to fight and to destroy the ability to make war is a modern concept.
I am not certain that we either minimize destruction or prevent suffering and loss of life. I am minded of the Star Trek episode A Taste of Armegeddon, in which the war drags on for 500 years because the warring civilizations have made it possible to do so neatly and cleanly. The sides finally enter into truce talks when confronted with the prospect of fighting real war, with real weapons, with the very messy results that follow.
Certainly points made on television shows in the asbtract feel different in the face of real corpses of children and burning buildings. They should. To view scenes of carnage and not feel revolted and sympathy for those slain is to lose an essential element of humanity. But the recognition that death and destruction are human tragedies does not make any alternative preferable -- especially when it amounts to little more than the same death and destruction on the installment plan.
The Romans did not break the rebellious spirit of Judea until the end of the Bar Kochba revolt. This amounted to ethnic cleansing of the province of Judea, the sowing of the Temple Mount with salt, an an effort to obliterate Jewish culture so thorough it included changing the name of the province from Judea to Syria Palestina. We do not, culturally, love the ROmans for this. But from the Roman perspective it was the only way to break the spirit of a rebellious province. And it worked extremely well. Jewish fighting spirit was so thoroughly broken that the concept of a Jewish state achieved and defended by force of arms did not become a serious consideration until the 19th Century.
War is ugly, cruel and destructive. But it is these factors that make it something to be so devoutly avoided. The deaths of a distant enemy are easy to contemplate. The utter destruction of of one's own home is much less easy to contemplate. The Palestinians attack civilian targets precisely because it is meant to weaken the Zionist oppressor will to fight. Israel pressures the Palestinian civilian population through economic embargo and willingness to engage Hamas militants despite the civilian deaths and destructions precisely because they want to break the will of the Palestinians to support armed resistance. Both sides are tough, stubborn, and convinced of the rightness of their cause. It is only the possibility of utter destruction and widespread slaughter that forces either side to even consider possible concessions.
I do not expect the Palestinians to see this as just. It isn't. It is no more just than was the utter destruction of Judea by Hadrian, or the destruction of Atlanta by Sherman, or the destruction of Dresden or Tokoyo or Hiroshima or Nagasaki. But I do not see what prompts one side to surrender to another without such tactics, or what else prompts governments and people to avoid war in the first place.