Marx and Engels were close confidants and had the same beliefs and aspirations.Both of them devoted a great deal of effort to Capital.Although Engels Tracksuit did not claim co-authorship of Capital, he was a genuine collaborator in ensuring it would appear, making major contributions to its creation and publication.
Together with Marx, he helped lay the foundations for Capital in the 1840s, establishing the basic elements of practice, method, and politics that would bring the work into being.From the 1850s to 1867 he devoted enormous energies to supporting the creation of Capital.During the 1870s he worked to promote Capital, and from 1883 to 1894 he toiled at preparing the Military Helicopter final two volumes for publication.
All in all, Engels was a legendary writer who devoted himself to Capital over a period of half a century.