... The Caribbean Sea and the Isthmus of Panama furnish the student of naval strategy with a very marked illustration of the necessity of such cohesion and mutual support between military positions assumed; as well as between those positions and the army in the field,—that is, the navy. It affords therefore a subject of the first importance for such a student to master, and that in fuller detail than is expedient for a series of lectures, the object of which should be to suggest lines of thought, rather than to attempt exhaustive treatment. For an American naval officer, the intimate relation of the Isthmus and its coming canal to the mutual support of the Atlantic and Pacific coasts renders the subject doubly interesting. This interest is yet farther increased by the consideration that the general international importance to commerce of such a point as the Canal can scarcely fail to make the conditions of its tenure and use a source of international difference and negotiation, which often are war under another form; that is, the solution depends upon military power, even though held in the background. There are questions other than commercial dependent upon the tenure of the Isthmus, of which I will not here speak explicitly. To appreciate them fully there must be constant reading and reflection upon the general topics of the day. One thing is sure: in the Caribbean Sea is the strategic key to the two great oceans, the Atlantic and Pacific, our own chief maritime frontiers. 12. PRINCIPLES OF NAVAL ADMINISTRATION _Opposing Elements_[34]