During the time when the Greeks and Persians were in constant wars, Pythia the then priestess of the temple of Apollo, was known for many of his prophesies, among which was the prophecy she made following the Greek defeat at the hand of Thermopylae and Artemisius.
In the prophecy, Pythia made it known that the Athenians should evacuate and that only a "wooden wall" would keep them safe.
After much deliberation, the Athenians concluded that the "wooden wall" of the prophecy means fleet of warships.
Eventually at the battle of salamis, it was with a naval warships the Athens resisted the opposing armies to overran them.
He didn't want to be so harsh, and knew they only were being mislead from the rich people making free labor off the slaves. Most of the confederates fighting hardly had slaves and barely shared any "racist pride". So Lincoln was Lenient.
