Sentence:  To my knowledge , Lincoln remains the only Head of State and Commander-in-Chief who , while <WSD>fighting</WSD> a fearful war whose issue was in doubt , proved man enough to say this publicly - to give his foe the benefit of the fact that in all human truth there is some error , and in all our error , some truth . 
Meaning of the word marked with <WSD> tags:  be engaged in a fight; carry on a fight