Volume 44 contains the letters of Marx and Engels from July 1870 to December 1873. The correspondence constitutes a valuable source for the study of the International Working Men’s Association in its final stages. Many letters deal with the Franco-Prussian War (1870-71) and discuss the military strategy and progress of the war. The letters contain valuable commentaries on the working-class movement in Britain, France, Italy, Spain, Russia and the USA. The letters show that Marx and Engels were engage in intense theoretical activity during the period of their leadership of the First International. The Appendices include letters by members of the Marx family.