Willie Shakespeare may have summed it up best when, borrowing the voice of King Richard III, he penned "A horse! A horse! My kingdom for a horse!"

History is replete with examples of how, but for the proverbial horse, kingdoms have been lost.

My reference point is an accident that will almost certainly lead to tragic miscalculations and havoc down the road. And, I might add, an exceptional opportunity for the patient and attentive investor.

It has to do with an impending shortage of easily accessible (read: inexpensive) oil to quench the insatiable thirst of the United States.

It's also connected to the inroads the cash-rich and geopolitically ambivalent Chinese - among others - have been making in building strategic relationships, and making direct investments, with the world's major energy providers.

With only so much oil to go around, every new off-take agreement signed by the Chinese with the Saudis or Venezuelans, for example, is a net loss in supply to other bidders, notably the world's largest energy consumer, the United States.

That the Chinese, and other countries, are aggressively securing long-term energy arrangements, coincidental with what appears to be an official U.S. diplomatic initiative to actively offend all the major energy producers, makes the securing of U.S.-controlled reserves and production critical.

The problem with cheap oil can be seen in the chart here.

And it has been confirmed in a recent report issued by the U.S. military, conveniently summarized by DailyFinance: "A recent Joint Operating Environment report issued by the U.S. Joint Forces Command suggests that the U.S. could face oil shortages much sooner than many have anticipated.

"The report speculates that by 2012, surplus oil production capacity will dry up; by 2015, the world could face shortages of nearly 10 million barrels per day; and by 2030, the world will require production of 118 million barrels of oil per day, but will produce only 100 million barrels a day."

Bottom line: The U.S. needs secure oil sources, and "on the double," as a military type might say. And so the pressure has increased for the U.S. government to remove its actual and effective regulatory bans on offshore drilling.

While it's more smoke than fire, the Obama administration recently made a tentative step in that direction - because even though its most ardent supporters may hate the extractive industries, Team Obama is not stupid enough to think that the energy gap is going to be closed by solar or wind power anytime soon.

Which brings us to the lost horse in this drama - the messy sinking of an oil rig off the coast of Louisiana, resulting in a spill of about 5,000 barrels, or 210,000 gallons, a day into the Gulf. It is estimated that it could take a month or more to cap the well.

The damage caused by this untimely sinking will extend far beyond wreaking havoc on the wildlife - the real importance is that it hands the luddites and enviro-fanatics just the ammunition they need to stick a brick wall in front of the baby steps underway for expanded offshore drilling. It is the equivalent of the accident at Three Mile Island, which set the nuclear power industry back by decades.

And that means precious time lost, and a near certainty that America will find itself hostage to the oil-producing nations in the years just ahead. That, in turn, means higher and higher prices, and hundreds of billions of dollars flowing overseas. Which, in turn, means a persistently high current account deficit, adding yet more weight to the pressure building on top of the U.S. dollar.

Even if the U.S. were to adopt the equivalent of a war footing in its quest for new offshore discoveries, the size of our steady demand assures that any new finds would still be insufficient over the medium to long term. If the military's assessment is even close to being on target - with global shortages appearing in four short years - then even the most urgent action taken today would prove woefully inadequate.

But the U.S. is not adopting anything remotely close to urgent action in the quest for new oil supplies. Quite the opposite. The administration and its well-meaning but ill-advised allies are advancing legislation to hinder and penalize virtually all the base-load power providers. And thanks to the poorly timed sinking of the Deepwater Horizon rig, the opponents of "dirty" energy have been provided with a powerful weapon to be used in challenging all new offshore drilling initiatives.

How to play it? First and foremost, you'll need to be patient. Oil prices aren't going to skyrocket overnight, and the base-load power industries - oil, coal, gas, and nuclear - will still have to struggle through the coming onslaught of politically motivated regulatory hamstringing. Between now and the time that the depth of the nation's energy problem becomes apparent to all, the energy sector will remain volatile.

The time to begin buying is when new legislation, coupled with a next leg down in the broader economy and markets, results in an across-the-board sell-off in the energy sector. That will be the time to get serious about building your energy portfolio. Between now and then, your goal should be to learn as much as you can about this critical sector.

And don't forget to include the oil services sector in your studies. That sector could be the poster child for "feast or famine." While the sector has bounced off its 2009 bottom, as the inevitable scramble for new offshore discoveries begins, the better-run companies will reward patient investors with multiples.

But first, thanks in no small part to the sinking of the Deepwater Horizon rig, the U.S. will take several steps back - away from anything that looks like energy security.

The single best way to stay closely in touch with energy and the many opportunities to profit available is with a subscription to Casey's Energy Report, headed up by the hard-charging Marin Katusa in close collaboration with Dr. Marc Bustin, arguably one of North America's top unconventional oil and gas experts. It is no coincidence that of 19 stocks Marin recently picked, 19 were winners... a 100% success rate. Click here for more.