THE CONQUEST OF CANADA! In the years after independence the subjugation of Britain's remaining North American colonies tantalized American leaders. Thomas Jefferson, for one, thought it was "a mere matter of marching." And why not? In 1810 Upper and Lower Canada had a population of 800,000; the United States boasted 7.5 million. The Yankees eventually did march-- in the War of l812--and they failed miserably. Thereafter the prize never seemed worth the effort, even in the most milita the Molson's.

In the struggle to repel the American invasion was a Canadian national consciousness born? This is the thesis of Pierre Berton's vividly written and immensely readable history of the War of 1812, begun last year with The Invasion of Canada: 1812-1813 and now completed with the publication of Flames Across the Border: The Canadian- American Tragedy, 1813-1814.

It is always salutary to read history written from the other side. Generations of midwestern and upstate New York schoolboys used to thrill to Oliver Hazard Perry's report of the Battle of Lake Erie: "We have met the enemy and they are ours." How many, then or now, know the (somewhat tame by comparison, to be sure) words of Gen. Sir Isaac Brock at Queenstown Heights on the other side of the Niagara River: "Push on, brave York Volunteers"? Yet Brock's exhortation to the Ontario militia at a stroke established the myth of a martial tradition in Anglophone Canada. The myth sent thousands of Canadians to die at Vimy Ridge and Dieppe in later and more terrible wars. Such is the stuff of national mythologizing.

Berton is a broadcaster and popular writer in his homeland. A previous book was the story of the Dionne quintuplets. This is not a background to impress professional historians. Like a suprising number of journalists he has read the masters and no doubt longed to write a definitive book himself. It is a pleasure to report that he has succeeded admirably. Flames Across the Border, like its predecessor, is drum-and-trumpet history at its best, beautifully researched, with plenty of desperate fights, besieged stockades, midnight marches, Indian massacres, and cannonades under clouds of sail across the waters of sparkling blue lakes.

Berton's narrative concentrates on the border war and hurries past political and diplomatic events. The war began on the high ground of national honor: American ships have been stopped on the high seas and American sailors impressed into the Royal Navy. The British announce they will cease this nefarious practice, but it is too late, Congress has already declared war. It is the first error in a succeeding tragicomedy of errors as two frontier societies attempt to organize for that most disorganized of human activities, mortal combat.

In 1813 the American strategy is simple. In overwhelming numbers American forces will cross the St. Lawrence and seize Kingston and Montreal, thereby slicing Canada in two. The other side musters a handful of British regulars, Tecumseh's confederation of Indians and a militia of dubious loyalty. But British elan, at Detroit, Buffalo, and Michilimackinac, grabs the initiative at the begining of the war and the Yankees are kept perpetually off-guard. The American commanders ineffectually struggle with overextended supply lines, the rigors of winter campaigning, and the impetuousness of irregulars ("Tarnation! Any Kentuck can lick 10 Indians!"). At the end of the war, despite naval victories at sea and on lakes Erie and Champlain, the Americans are faced with bankruptcy, a burnt and sacked Washington (in retribution for the burning of York, Ontario) and an enemy being massively reinforced with the cream of Wellington's veterans. It will be 30 years before the Americans embark on another foreign war.

Berton writes very well when he describes actual campaigns and the personalities of the combatants. Regard the Americans moving against Montreal in October 1813: "The valley of the St. Lawrence is bathed in an Indian summer glow as six thousand men in 350 boats, forming a procession five miles long, slide down the great river, flags flying, brass buttons gleaming, fifes and drums playing, boatmen chorusing." In this glorious pageant, however, all is not well. Some of his officers think the American general, James Wilkinson, is drunk. Most likely he is under the influence of opium, prescribed to ease his dysentery, an ailment that has now spread to most of the older officers in the American command. Soon the flotilla slows to eight miles a day. Under fire from every bush at every twist in the channel, as the aroused Canadians, French and English alike, take to arms, Wilkinson loses his nerve and orders a retreat.

Even today we can see why. There is something unnerving to the American traveler about the Canadian landscape. It has always struck me immediately on crossing the border. Is it the sense of desolation, the hint of an Arctic chill in the air? Or that boundless forest, an immensity captured so perfectly in Francis Parkman's classic account of war in the North Woods and the two-century struggle of Englishman and Frenchman for the control of New France?

In Berton's narrative, new characters march through the wilderness in the footsteps of Pontiac, Wolfe and Montcalm. They will please persistent readers of military history, who perhaps know their American Civil War but not this war. Among the portraits are those of Winfield Scott (so gallant and impetuous, how could he become the "Old Fuss and Feathers" of 1860?); the noble Tecumseh, sans peur et sans reproche, whose defeat and burial in a secret grave at the Battle of the Thames destroys forever the power of the eastern Indian tribes, and the Rev. John Strachan, future Anglican bishop of Toronto, one of a number of patriots who will ensure that Canadian society becomes "more concerned," says Berton, "with peace, order and good government" than with "life, liberty and the pursuit of happiness."