And what more natural connection can there be between any two ideas than between those of common defense and general welfare, since the general welfare of no country has ever continued long unless it was defended.
Now the general welfare of every maritime power has always been intimately concerned with its sea-borne commerce.

It is only by means of sea-borne commerce, for instance, that Americans can live in the way Americans wish to live.

"General welfare" means more than mere existence.

A mere existence is the life a savage lives.
Furthermore, the general welfare of a country requires the safety of its exported and imported goods while on the sea, and includes the right of its citizens to travel with safety in every land, to buy and sell in foreign ports, to feel a proper measure of self-respect and national respect wherever they may go, and to command from the people of the lands they visit a proper recognition of their claims to justice.
Naval defense may, therefore, be said to consist of three parts: 1st--Defense of the coast against bombardment and invasion.
2d--Defense of the trade routes traversed by ships carrying the exports and imports of the country.
3d--Defense of the national policy, including defense of the nation's reputation, honor, and prestige.
Of these, defense of the coast against bombardment and invasion is the easiest, and defense of the national policy the most difficult; because in preventing bombardment and invasion the defender has the strategical advantage of being nearer home than the adversary; while in the defense of a country's policy, a naval force may have to "assume the offensive," and go even to the far distant coasts of the enemy--as the Russian fleet went to Tsushima, where it met its death.
In that part of naval defense which is concerned with trade routes, the strategical advantage must go, in general, to that side which is the nearer to the locality where the decisive battle may occur.
In laying down a policy of naval defense, however, it is not necessary to consider these three parts separately, because no nation can ever tell whether in the distant future its naval defense will have to be used directly for any one of the three, or for all.
In general terms, it may be stated that in nearly all naval wars the fleet has been used more for the defense of the nation's policy than for the actual defense of the coasts or the trade routes.

This does not mean that there has never been a bombardment or invasion, or that the defense of trade routes may not have been the cause of the war itself; but it does mean that in actual wars bombardment or invasion has been rare, the capture of merchant vessels has played a minor part, and the deciding events have been battles between two fleets, that were often far from the land of either.
Owing to the fact that within modern times most of the important countries of the world have been those of continental Europe, with frontiers contiguous, and in fact identical, the defense of a country has been largely committed to the army, and most of the wars have been on land.