Seeing the Chinese-Vietnamese border from both sides is like seeing matter and antimatter; seeing Tweedledum and Tweedledee; seeing double.

The Chinese will tell you that the Vietnamese lob mortar rounds onto Chinese farms and villages and shoot at Chinese farmers and plant land mines, and that only when attacked in this way do they -- the Chinese -- respond in kind.

The Vietnamese will tell you that the Chinese lob mortar rounds onto Vietnamese farms and villages and shoot at Vietnamese farmers and plant land mines, and that only when attacked in this way do they -- the Vietnamese -- respond in kind.

On the Chinese side of this disputed border, 90 miles from Hanoi, dwell the Zhuang, a minority people who characteristically dress in black and speak their own dialect. On the Vietnamese side of this same border are the Nung, a minority people who characteristically dress in black and speak their own dialect. Culturally and linguistically the Zhuang and Nung might be one people.

On the Chinese side are trim military cemeteries of white concrete gravesites with red stars and red letters signifying the fallen patriot. On the Vietnamese side are trim military cemeteries of white concrete gravesites with red stars and red letters signifying the fallen patriot.

And so on.

If there is an essential difference it is that during late February and early March 1979 there was a short, savage border war between these countries and in that war the Chinese rained havoc on the Vietnamese border villages and towns. One such town is Lang Son, 12 miles from the border on the invasion route to Hanoi.

The war began on Feb. 17, 1979.

"The Chinese," claims Lang Son official Ba Kim Thinh, "intended after 24 hours to occupy Lang Son. . . . It took until March 3." Contemptuously, he added, "more than 24 hours." Also, the Chinese never fully occupied Lang Son -- just half of the town.When they withdrew on March 3 they blew up and booby-trapped their half of the town. They also retreated with a very bloody nose.

Thinh is quick to recite the inventory of outrage: 200,000 Vietnamese were evacuated from the province; 565 civilians were killed, including 226 women and 113 children; 20 factories were destroyed, along with 72 kindergartens, 30 schools, 61 shops, five hospitals. Land mines claimed another 119 civilians killed and 235 injured and the loss of 500 water buffalos.

For their part, says Thinh, after 16 days of fighting, the Vietnamese killed or wounded 20,000 Chinese soldiers and destroyed 132 military vehicles and 70 tanks.

What were the Vietnamese military casualties? Thinh doesn't know.

Lang Son's opposite is a town in China called Pingxiang. Pingxiang is on the same highway and rail route to Hanoi. Both towns have light industry. Both are market towns for the innumerable surrounding agricultural communes and state farms. Both have large numbers of minorities. Indeed, before February 1979 there was considerable traffic between the two communities as townsmen and peasants traveled back and forth visiting relatives and buying consumer goods.

Now traffic is halted, except for the tiny trickle of Vietnamese who sneak out of their country to find sanctuary in China.

To get to Lang Son one must travel by car. It is roughly a four-hour journey from Hanoi. Surprisingly, the road is well paved, albeit studded with intestine-bending potholes. In contrast, the Chinese counterpart highway is badly maintained and in continual repair.

Along the route one sees what Vietnam is mostly about -- an obsession with food, whether it is growing or cultivating or harvesting or marketing or preparing it. One sees, too, the ravages of wars past. Bridges bombed by American B52s still are down, for example. One also sees the constant reminder of Vietnam's war footing psyche in the guise of military cemeteries and war memorials commemorating victory over various enemies and in propaganda billboards now exhorting youth to be vigilant against the Chinese.

Not surprisingly, too, in this mirror world there are the requisite radars, antiaircraft batteries, airfields and Army bivouacs approximately the same distance from the border as are their Chinese counterparts.

But, for quintessential symbolism on the way to Lang Son one stops at a cut in the highway -- just about where the wild sunflowers are most prevalent along the highway and where the small but formidable mountains loom out of the earth -- to pause at Chi Lang pass, roughly 30 miles from the border.It is here, at this pass, that twice in Vietnam's 4,000-year history the Vietnamese stopped Chinese invaders.

An Army colonel who has fought the Japanese, the French and the Americans says it is not easy for the Chinese to start another war.

"Their leadership is not stable," he says. "If they start a big war they will have to mobilize everyone. It costs a great deal of money to start a war. Surely the divisions they showed us [in the 1979 border war] were not very good. At Chi Lang, where we defeated them twice, they lost 100,000 men each time. We will defeat them again."

Two young foot soldiers were equally cocky about defeating the Chinese in any future encounter. The soldiers were at a checkpoint a kilometer from Dong Dang near the border itself. This was the closest the Vietnamese would allow a foreign reporter to get to the border, unlike the Chinese who marched foreign correspondents right up to the imaginary border line. The Vietnamese explanation for their reticence -- if the Chinese saw the "big nose, the white skin, the Western clothes, they would think you are a Russian adviser and shoot you."

One of the young soldiers, the one obviously in charge that day, said he didn't know why the Chinese attacked Vietnam in February 1979 but "history tells me that the Chinese are expansionist." Asked how good were his Chinese adversaries, he replied, "so-so."

He is ready for another battle. So, too, are the young men of China's People's Liberation Army a dozen miles away.