Old English—early in its existence—did not differ much from its Germanic cousins. In fact, these languages could be considered distant dialects from one another. However, through the course of its development, Old English lost part of its Germanic morphology: the case-marking system. The loss of this system had such an impact on the development of the language that the results are seen in Modern English. This paper examines these results, and to an extent the reasons, behind this reduction.
Walters, Denise E.
"Loss and Consequence: An Examination of the Old English Case Marking System As Opposed to that of Other Old Germanic Languages,"
Colorado Research in Linguistics: Vol. 17.
Available at: https://scholar.colorado.edu/cril/vol17/iss1/7