"The workingmen of Europe feel sure that, as the American War of Independence initiated a new era of ascendancy for the middle class, so the American Antislavery War will do for the working classes. They consider it an earnest of the epoch to come that it fell to the lot of Abraham Lincoln, the single-minded son of the working class, to lead his country through the matchless struggle for the rescue of an enchained race and the reconstruction of a social world" - Karl Marx, letter to Abraham Lincoln on behalf of the International Workingmen's Association, January 28, 1865 (located in Collected Works of Karl Marx, Volume 20, page 19)
Now, I do not know what your previous familiarity with Marx's writings may be though I do advise them to any fellow conservative as a central part of the "know your enemy" principle. When reading them there are a few things you should always know. Marx uses many buzz words, such as "working class" and "working men." When mentions the "working men" rising up, he's talking about a communist revolution of the proletariats. When he mentions an "era" of the "working men," he's talking about an era of communism. When he mentions a "struggle" of the "working men," he's talking about the plight of the proletariat that, in his mind, will lead to communism. When he mentions redefining the social order of the world, he's talking about redefining it toward communism. As you should be able to see with ease, he uses all of these terms in his praise for The Lincoln.