CONSIDERING that the United States does three times as much trade with Taiwan as with mainland China, it is clearly not present or even prospective trade that took the President of the United States to Peking last week.
The best way to get the trip in perspective is to refresh our memory of things that happened in the same part of the world awhile back.
On Jan. 30, 1902, Great Britain signed a ''defensive treaty of alliance'' with Japan. The Encyclopaedia Britannica gives as the reason for the treaty ''the threat of Russian aggression in Manchuria and Korea.''
Czarist Russia 100 years ago was just as expansionist as the Soviet Union is today. Russia was pushing outward then just as it pushes outward now, and in much the same directions. A main preoccupation of British foreign policy during the later years of Queen Victoria's reign was the ''containment'' of Russia.
The British, along with the French, landed an army in the Crimea in 1853 to relieve Russian pressure in Turkey. During the rest of the century the British worried about the Russians breaking down to the Indian Ocean through what is now Afghanistan, Iran, and Pakistan. The British sent expeditions into Afghanistan, primarily to get there ahead of the Russians.
The Afghans were able to take care of themselves in those days. Both Russian and British excursions into those high mountain valleys came to grief. The British Army once occupied Kabul.
By 1900, China was in a state of anarchy. It was incapable of defending itself. The European maritime powers grabbed ''treaty ports'' along the coast and maintained substantial forces in Peking to protect ''the legation quarter.'' The Russians came from overland. They consolidated the present maritime provinces of Siberia. They moved down through Manchuria to the coast at Dairen and Port Arthur. They began pushing into Korea.
The British looked around for local help to contain Russia's push into Asia. The British had sea power, but nothing like enough manpower to be able to challenge Russia on the far side of the world. The answer to their problem was the treaty of alliance with Japan, which remained in force from 1902 to 1923. In 1904 the Japanese attacked Russia.
The 1902 treaty with Japan achieved Britain's purpose. It stopped Russia. The Russians made no further gains in China or at China's expense until the end of World War II.
Russia was contained in those days by Japan in the Far East; by the Indian Army, under British control, in the Middle East; and by the rising power of Germany in Central Europe.
Times change. Britain no longer controls the Indian Army. Japan no longer has the ability to handle Russian power in Asia by itself. The United States has taken over much of the former British role and is the country most actively occupied now in planning the containment of Soviet power.
The NATO alliance has taken over from Imperial Germany the role of containing Russia in Central Europe. The new US relationship with China, added to the older relationship with Japan, is a mighty barrier in Asia. Japan and China together, both backed by the US, are more than sufficient to the task. The only open frontier the Soviets have now is in the Middle East.
And that is not as open as it might seem. India joins China in protesting against the Soviet presence in Afghanistan. Moscow cannot regain the confidence of either India or China unless it gets out of Afghanistan and refrains from moving into Pakistan and Iran. The US is not the only country with a lively interest in the containment of Soviet power.
There is no ''defensive treaty of alliance'' between the US and China. The wording would seem outdated for these times. But that was the inner meaning of President Nixon's trip to Peking in 1972. The implicit treaty of 1972 was renewed last week by President Reagan. China is today's main barrier to Russian expansion into Asia.