DETROIT (Bloomberg) — When the history of the U.S. auto industry is written, a few pages should be devoted to Toyota Motor Corp.’s new pickup-truck assembly plant in Texas and the threat it poses to Detroit’s last profit stronghold.Not much is subtle about pickup trucks and the same can be said for Toyota’s $1.28 billion factory in San Antonio, built on a 2,000-acre former cattle ranch. The plant also represents a shift for the Japanese automaker, which has spent 50 years trying to avoid antagonising trade relations with the US.

But once Toyota proves, as it will soon, that it can sell full-size pickups to cowboys, farmers and ranchers in Texas — where more of the vehicles are sold than anywhere in the US — its low-profile days will be gone forever.

A half-century ago, Toyota imported its first sedan to California. By the mid-1980s, the United Auto Workers union was bashing Japan rhetorically and enlisting its allies in the US Congress to enact protectionist legislation. Two weeks ago, the first Tundra pickup-truck rolled off the San Antonio assembly line, a model big and powerful enough to stack up against trucks built by General Motors Corp., Ford Motor Co. and DaimlerChrysler AG’s Chrysler Group.

The Tundra is set to plant a flag in the one segment of the market US automakers have had mostly to themselves. About one out of nine vehicles sold in the US is a Chevrolet Silverado, GMC Sierra or Ford F-Series pickup. When Toyota in 1993 introduced the T100, its first truck portrayed to be “full-size,” it was consciously designed to be smaller and less powerful than the U.S. competition. Why? I often asked company executives.

They replied in their usual self-effacing way that Toyota knew little about large pickups, which aren’t sold to the masses anywhere except in the US.

Toyota’s smaller compact pickup was fine for most of its truck customers, they said.

Meantime, the Japanese automaker noticed that owners of its cars were buying competitors’ large pickups because Toyota didn’t make one. “We wanted to give Toyota owners a vehicle so they could stay with Toyota,” said company spokesman Irv Miller. “We don’t think many of our future sales will be conquests from Ford and GM.”

Toyota executives don’t want to be seen as poachers. They realise the domestic automakers now cling to life by virtue of pickup sales, which remain profitable. Detroit’s other vehicles already are getting clobbered by Toyota Camrys and Corollas, while Toyota’s Lexus division has surpassed GM’s Cadillac and Ford’s Lincoln luxury brands.

The Tundra pickup that replaced the T100 in 1998 still was a tad smaller than peers from GM, Ford and Dodge. Toyota deliberately opted for modesty in a category characterised by macho boasting about size, toughness and power.

Toyota is after Detroit’s business, though it doesn’t want Detroit out of business. Piling up sales too quickly, coupled with a bankruptcy of one or more US rivals, might trigger a political backlash. No one at Toyota’s headquarters in Japan has forgotten the “voluntary” government restraints on exports that the company was forced to accept in the 1980s to ease trade tensions with the US.

Years of steady, measured growth created strong and growing profitability. On November 7, the automaker predicted it will earn more in its current fiscal year than any Japanese company ever. Net income is forecast to rise 13 percent to 1.55 trillion yen ($13 billion) in the year ending in March.

Toyota has 15.2 percent of the US market and is poised to surpass GM within two years as the biggest seller of vehicles in the world.

Part of the growth will surely come from the San Antonio pickup plant, which will be able to produce 200,000 Tundra trucks annually when it reaches full capacity in 2008.

Added to the 100,000 Tundras that Toyota can build at its Princeton, Indiana, factory, the Japanese automaker’s full-size pickup volume still will be only about a third that of either Ford or GM. Toyota professes no ambition of passing Ford or GM in terms of vehicle sales in the US in the foreseeable future.

Instead, by keeping costs low and production goals in check, Toyota can set the price of its new truck relatively high when it wants to generate maximum profit — or lower when it wants to stoke consumer demand. Fully loaded pickups can command prices of more than $40,000.

If Toyota wins premium status in the segment, US automakers might see prices on their pickup models forced down by comparisons with Tundra, which probably will earn high marks for quality, reliability and resale value. No one can predict how well Tundra will sell, though if history is a guide, the automaker’s extensive research and preparation, on top of the clamour for a new truck by its dealers, suggest that Toyota’s sales goals are conservative.

“Toyota’s secret is that it executes extraordinarily well,” said Noel Tichy, a professor of organisational behaviour at the University of Michigan. “It’s not rocket science. You knew the big truck was coming six years ago.”

This is a company that worries mostly about complacency. Barring events unforeseen, the only limits that Toyota faces in the next few years are ones it puts on itself — to ensure it doesn’t thrash competitors in too unseemly a fashion.Doron Levin is a Bloomberg News columnist. The opinions expressed are his own.