Quote From the emancipation proclamation: what does this mean?

Question

“…And, upon this, sincerely believed to be an act of justice, warranted by the Constitution, upon military necessity, I invoke the considerate judgment of mankind and the gracious favor of Almighty God.”

Answer 1

It does NOT mean that he had to do it for political reasons; I think that's a cynical response.  It was not only moral and just, it was also a strategic military move.  

If it was "sincerely believed to be an act of justice, warranted by the Constitution," Lincoln believed Emancipation to be the right thing to do, and that by doing it, he was upholding his oath to defend the Constitution.  "Upon military necessity" is the strategic part.  If slaves could escape to the North and be freed, then the South would be hurt both militarily and economically.  

"I invoke the considerate judgment of mankind and the gracious favor of Almighty God," is a plea to the people to stand behind him, and a prayer to God to do the same.  

Answer 2

Yikes

I think that it means something like,

"I ask God and mankind to look favorably on this action, which is taken as an act of justice and is required by the constitution."  Like, 'I have to do this for political reasons (free the slaves), but I am hoping that people will approve."