Despite an uncertain future and changes throughout history, sea power as an instrument of defense and global influence endures. It endures because the sea remains the domain of commerce, communications and resources, and it endures because sea power has proven, over the course of history, to be a flexible, adaptable, rapid reaction force that a nation can use regardless of time or situation – as long as the right capability and capacity exist.

The flexibility and the rapid response inherent to sea power will grow more important as uncertainty prevails and the resources available in the global commons at sea become more dear.

Consider, for example, the naval capability of power projection. The old image of power projection comes from the black and white grainy films of Normandy. Power projection was certainly useful then, but what does power projection mean today?

The launching of 75 percent of strike sorties from the sea in the opening days of the war with Afghanistan; the striking of terrorist camps from ships and special operations force formations from sea; or the storming of the beach, not with tanks and guns, but with food and water to relieve the people of Indonesia, Sri Lanka, Thailand and Haiti – that is power projection from the sea.

Power projection is an old concept – and many people think that it belongs to history – but its utility endures to this day. From launching strikes, to launching disaster relief, to launching evacuation missions, the need to project power will grow in our disordered and easily disrupted world as populations migrate to the coasts; climate change pressurizes and imperils coastal populations; and a large presence on land becomes politically problematic or internationally uncomfortable.

But sea power isn’t just about power projection. Consider the age old naval task of convoying and, conversely, intercepting enemy goods. This was something we did to counter the Barbary pirates in the 19th century and a tactic in World War II.

And now? There were the Tanker Wars in the ‘80s in the Arabian Gulf, fought to protect trade and preserve the flow of oil coming from the Gulf as Iran and Iraq sought to destroy one another. There is Joint Interagency Task Force South that intercepts the illegal flow of narcotics coming via speed boat and semi-submersible. There is the global Proliferation Security Initiative that aims to prevent and interdict the trafficking of weapons of mass destruction that are most easily transported via the sea.

And if you think the value of convoying or protecting trade has diminished, consider the Gulf of Aden: while it is not convoying in the most traditional sense, suffice to say that the threat of pirates against commercial shipping was enough of a concern to bring together an international fleet of ships to protect it.

Ninety percent of intercontinental trade moves on the surface of the seas and a further $3.2 trillion dollars of trade swims with the fishes in undersea cables that lace the ocean floor. The value of sea power – of protecting legitimate trade and interdicting illegal trade – remains.

What of logistics? Ninety percent of military materiel in Desert Shield and Desert Storm came over the seas and 95 percent of what came back travelled on the sea.

Ballistic Missile Defense is another good example. To go from covering the Western Pacific to defending the Mediterranean, give me the transit time and I can give you a first class Aegis ballistic missile defense ship on station without the need to infringe upon the sovereignty of any nation. To achieve the same effect on land, you’d have to negotiate for a new base and arrange for no less than 35 lifts of C-17s from the Western Pacific to that Mediterranean location.

The effects that only a naval force can deliver are as relevant to the future as they were to the past. Indeed, I believe sea power will be even more relevant.

Take hybrid war, the term du jour for the wars that we are in and those we are likely to face: riverine operations and riverine squadrons, so useful in Vietnam, are again at work in Iraq; power projection from the decks of our carriers in the North Arabian Sea is literally a lifesaver for troops on the ground in Afghanistan; and maritime interdiction of the flow of money, equipment, and terrorist personnel remain as relevant as they did for a state in the days of sail. The Mumbai terrorists did not come across the border, they came from the sea.

Even the very nature of our operations – ships operating and communicating across long distances – has positioned us well for the cyber challenges that are likely to grow in the 21st century. In fact, I have recently reorganized the Navy Headquarters by merging the command, control, communications directorate with our intelligence and information directorates into one, and we’ve created Fleet Cyber Command/10th Fleet, to bring our cyber capabilities together to improve them for the future.

Beyond the interdictions, beyond the power projection, beyond hard power entirely, however, we cannot forget the uniquely diplomatic nature of a navy.

We can send a force, large or small, to the international waters off the coast of any nation and have our presence felt; we can change the calculus of international decision making. That option is unique to a naval force, because a response in the skies cannot be sustained long-term and a landward response can challenge diplomacy as much as it can promote it.

We can also conduct diplomacy at sea. We can send a destroyer or a frigate to operate with a PLA navy ship in the Gulf of Aden to counter piracy and in turn improve the communication and understanding between our navies and our nations.

I can even send an amphibious ship to the Gulf of Guinea, to go ashore to deliver humanitarian aid and encourage the development of local maritime security capabilities, such as fisheries protection for states that need that to fuel their economy.

The uniquely diplomatic and preventive nature of sea power is as important to the prevention of conflict as it is to winning in conflict.

Indeed, the recent U.S. Department of Defense Quadrennial Defense Review not only recognizes the enduring quality of sea power as a tool of diplomacy and power in the 21st century, it has validated the strategy that we laid out two years ago in our Cooperative Strategy for 21st Century Seapower: a strategy that places equal importance on preventing wars as it does on winning wars; a strategy that fosters global maritime partnerships to increase understanding among nations and confront common challenges in the global commons; and a strategy that keeps in the forefront the capabilities that have served our navy so well throughout history and will no doubt be of greater importance in the future – that of having forward presence, providing deterrence, providing sea control, delivering power projection, conducting maritime security and humanitarian assistance and disaster response.

To imagine that sea power will somehow become less relevant in the 21st century is certain folly.

As a nation with 58,000 kilometers of mainland coast and a significant continental shelf, the value of sea power could not be clearer to Canadian strategists. Over its 100-year history, Canada’s navy has gained a reputation for being tough, for being professional, for punching well above its weight. It is also in rare company as a navy that truly has a global focus.

Despite all that the Canadian navy has done – that navies all over the world do – it is sometimes difficult to appreciate, as Admiral Dean McFadden has put it, the maritime blindness that affects many nations. A navy ship is seldom beloved when it is consuming your budget faster than it is consuming any enemy. Yet as historian C.P Stacey put it, “armies are improvised much more rapidly than navies, and a coast which is undefended in peacetime will be undefended in war.”

Budgets have never made navies popular. Yet a navy needs ships to have sea power. And, just as important, a navy must have an industrial base that can build those ships. As the Chief of Naval Operations in the United States, I think about the health of our shipbuilding industrial base often. No navy has ever been, or ever will be, great without a shipbuilding industry equal to its ambitions.

I cannot say with any certainty what the 21st century holds for Canada or for the United States. But I can say that despite this uncertain future, the value of sea power will endure and grow because it is flexible and adaptable. It will endure in its value to the nations that possess it, and moreover, it will endure in its value in our globalized world. The challenges and uncertainties in the global commons are too great for any one nation to shoulder.

Indeed, the world needs the Canadian navy’s help to maintain the fragile world order upon which we all rely. Canada and the world need Canadian sea power for the 21st century.

Admiral Gary Roughead is Chief of Naval Operations for the United States Navy. This article is adapted from a presentation to the Conference of Defence Associations.