You've posed an interesting question, but here's my problem with your premise.

As a contingent result of the war, slavery ended in the United States. However, the end of slavery in the Southern states didn't emerge as a Northern war goal for quite some time. President-elect Lincoln and others attempted to side-step the slavery issue in 1861. You're familiar with the effort to placate Southerners before Fort Sumter by enacting the so-called Corwin Ammendment. The proposed ammendment would have protected slave property in the United States from any legal restrictions.
http://en.wikipedia.org/wiki/Corwin_Amendment

Was there a war to abolish slavery during the modern era? Other than the slave revolt in Haiti, I cannot think of an internal war fought against slaveholders, or of a country making an attack to end slavery in a foreign land. What have I overlooked?