The need for an adequate defense of the nation's capital became desperately apparent on the evening of Aug. 27, 1814.

Looking up the Potomac that day from Fort Warburton about 15 miles south of the District on a peninsula jutting from the Maryland shore, the American commander of the fort, Capt. Samuel Dyson, could see smoke rising from the smoldering ruins of Washington. The British had successfully fought their way into the city several days earlier and set fire to the White House and Capitol, among other buildings, leaving a trail of devastation.

Less than three miles down river, near George Washington's estate at Mount Vernon, Dyson saw a fleet of British warships moving north. He was also hearing rumors about ground forces approaching from the rear.

With his small fort undermanned and open to attack from river and land, Dyson made a fateful decision. Evacuating his men, he ordered Fort Warburton blown up so it would not fall into British hands. He used the 3,000 pounds of cannon powder stored inside to do the job.

Thus fell the only structure existing at the time to defend the capital. The War of 1812 had clearly demonstrated how vulnerable Washington really was. Within weeks of the destruction of Fort Warburton, Fort Washington began to rise from its rubble.

Today, looking out over the parapet of the imposing structure, the view that Dyson found so ominous is serene. Pleasure craft glide along the placid river. On the opposite shore, nothing is visible except trees and a glimpse of Mount Vernon. The Washington skyline peeks out in the distance as a reminder of why the fort was built in the first place.

History and nature unite in this 340-acre national park. The fort is but one element, albeit a storied one. In September 1814, James Monroe, secretary of war and future president, hired Pierre Charles L'Enfant, the French engineer who had drawn up plans for the District of Columbia, to build a new fort above the site of the old one.

The relationship proved testy, however. Monroe questioned the expense of the project and demanded detailed plans and accounting. Insulted, L'Enfant refused to comply and was dismissed in 1815.

By this time, the war had ended, and construction of Fort Washington was deemed less urgent. The large stone-and-brick structure with the hornwork design -- so called because its northwest and southwest demi-bastions stick out like horns on the head of a bull -- was completed in 1824 and outfitted with approximately 80 cannon and space for 50 to 100 troops. Various improvements were added as the Civil War approached.

In the early years of that great conflict between the states, Fort Washington was the only defense point for the capital. Its strategic location high above the Potomac allowed control of movement on the river, something not to be underestimated when the most populous slave state and heartbeat of the Confederacy was just across the water. The fort served another function, too.

"We were important during the Civil War as a symbol," park ranger Don Steiner says. "We were an image of strength that people in Alexandria and D.C. could see."

Today, visitors to the park can see how soldiers stationed at Fort Washington lived during the war. Special programs there include artillery demonstrations, "living history" presentations and other regularly scheduled activities.

There also are guided tours every Sunday at 2, 3 and 4 p.m. Otherwise, visitors can take self-guided tours and see, for example, the cells used for holding men imprisoned by orders of the commandant or see various casements in which the fort's great guns were mounted.

Beyond the fort, natural beauty abounds. There are, of course, the magnificent vistas. Though the serenity is somewhat disrupted temporarily by road and parking lot improvements, the park offers extensive walking paths and picnic areas.

Dotting the grounds are concrete batteries built at the turn of the century for improved coastal defense. Although constructed away from the riverbanks, the rifled cannons once mounted in these structures could penetrate the armor plate of enemy ships at a much greater range.

The visitor center, completed in 1821 as the living quarters for the fort commander, contains exhibit rooms and an audiovisual program about the park. It also houses a gift shop with information about Fort Washington and other regional attractions.

Although a certain amount of decay resulting from a limited budget is evident throughout the park -- from crumbling mortar to peeling paint -- it does little to diminish the historical value and natural beauty of an infrequently visited resource.

PLAN YOUR EXPEDITION

Fort Washington lies on the Maryland shore of the Potomac River, south of the District. From

I-495, the Capital Beltway, take exit 3A to Indian Head Highway (Route 210). Drive four miles south on Indian Head Highway and turn right onto Fort Washington Road. Proceed 3.5 miles to the park entrance.

The entrance fee is $4 per vehicle, which allows unlimited access for three consecutive days.

Living history and other special programs are scheduled most of the year. Call 301-763-4600 for a schedule of events. The park emphasizes strict safety standards during artillery demonstrations.

Picnicking, hiking and fishing along the Potomac are popular activities. Call to reserve picnic areas in advance.

The park is open every day of the year. The fort and visitor center are closed on Christmas and New Year's Day.

CAPTION: This 24-pounder gun was one of several mounted on the frontal defense of Fort Washington in 1861.

CAPTION: An 1872 engraving of Fort Washington from Picturesque America.