In the Age of Sail, officers in the Royal Navy developed a (probably exaggerated) reputation as sadistic disciplinarians. Refractory sailors were flogged on the main deck, with the crew assembled to bear edifying witness. But when officers gathered below to share port—more refined stuff than the grog rationed to seamen—brutality yielded to gentility. Port-drinking customs observed today apparently stem from naval traditions. Decanters circle the table clockwise, port passing to "port," the nautical left. Should it stall, a tablemate might ask, "Do you know the Bishop of Norwich?" If the clueless tippler replies no, he'll be told, "The Bishop's an awfully nice fellow, but he forgets to pass the port."

Contemporary landlubbers will most likely find port served with cheese courses or the kind of hearty desserts (think plum pudding) that accompany holiday feasts. Port, of course, hails from Portugal and takes its name from the city of Oporto. But port's conventions have understandably British inflections. Conflicts between England and France in the late 17th and early 18th centuries halted Britain's importation of French wine and forced merchants to seek supplies elsewhere. In the hot, mountainous region up the Douro River from Oporto, they found a source of dark, coarse wine the English initially called "blackstrap." Following the practice of one particular Douro abbey, the English began adding brandy to unfinished wine, which both stabilized it for transport and arrested fermentation while keeping grape sugars high. The resulting "fortified" wine, sweet and alcoholic, launched an industry. 

Shippers with names like Cockburn, Graham, Osborne, Sandeman, and Taylor—many of whose brands and descendants still dominate the trade—built large "lodges" for aging and warehousing port in and around Oporto. Business flourished, and the drink's popularity in Britain grew to such a degree that port became known as "the Englishman's wine," imbibed "everywhere from gentlemen's clubs to street corner pubs," according to The Oxford Companion to Wine. Victorian men of station customarily laid down casks for their sons and godsons. (Unfortunately for me, this tradition was lost upon Irish-American fathers and godfathers of the late 1950s.) Over the past generation or so, consumption in other countries (including, ironically, France) has matched or exceeded England's. But the British market remains central to the trade, especially for high-end ports.

Port relies primarily on five grapes: Tinta Barroca, Tinta Roriz (the Tempra-nillo of Spain's Rioja), Tinto Cão, Touriga Francesa, and Touriga Nacional. They grow on narrow terrace vineyards carved into the steep, stony lands along the river. For centuries, little changed in the labor-intensive production of port, but recent decades have ushered in innovations. Laser-guided bulldozers grade new terraces, notes wine-scribe Hugh Johnson, and in one of the last wine regions that employs humans for grape-stomping, robotic feet now do much of the work.

Port comes in a confusing array of styles, with a heady-sweet profile the sole constant. Rough-and-ready rubies and tawnies account for the bulk of commercial production. Age-designated tawny ports mature in wood casks for longer periods and offer more of the nuances prized by port fanciers. Their label-specified age (usually ten or twenty years) indicates an average of the blend. Connoisseurs covet vintage port, made only from wines of a single year that producers have declared exceptional. After two or three years in cask, vintage port is bottled; it can—arguably must—age for decades to express its character fully. Late Bottled Vintage port (or "LBV") combines methods: Wine from a single year sees four to six years in cask before bottling and is then usually ready for consumption. Other port styles vary on these themes. Limited amounts of quaffable white port are produced.

Showing light, copper-toned ruby, Dow's Aged 10 Years Old Tawny Port ($26, 20 percent alcohol) offers aromas of golden raisin, nectarine, plum brandy, and fig cake. Medium-bodied and savory-sweet, its light prune, orange peel, and toffee flavors carry hints of tobacco and Dr Pepper, finishing on a sherry note. The English, God rest them, have also given us Stilton, a magnificent blue cheese. Pair it with port to guarantee a happy Yuletide.