I knew the Civil War Union Army used instant coffee but hadn’t realized it was a paste made from condensed milk (with sugar) and coffee.
I’ve never heard that. The Union guys were issued (when they could get it...) coffee in green bean form. I think it was a pretty sought after commodity, and lots of substitutes or ersatz tried, especially, in the Confederate side. Chicory, for example. The “Blue Bellies” had coffee, and “Johnny Reb” had tobacco ... so lots of informal (decidedly against regulations) trading went on.