In an expeditionary age where the modern emphasis is upon joint operations, it is easy to forget the extent of the contribution that naval forces may make, and indeed need to make, to the successful conclusion of operations ashore. This Letort Paper focuses on the modern concept of sea-basing but argues that in an era of naval transformation, it is important to remember that the maritime effect on land operations is far greater than that. The author, Dr. Geoffrey Till, demonstrates that point by making extensive use of allied, and particularly British, experience to set alongside American views and uses his subject to investigate the whole concept of naval transformation in the early 21st century. His conclusion is that, while there certainly are novel aspects to sea-basing, the concept, if not the words, would have been familiar to the navies of the past.