With the improvement in law enforcement after the military takeover five months ago, narcotics police have started seizing heroin at a record rate in Turkey, which is the main artery for the flow of heroin to the United States and Western Europe from Iran, Afghanistan and Pakistan.

In the last four months, police have seized 88 pounds of heroin, an opium derivative, with a street value of $8 million in New York.

"This is a record amount," a senior police officer said. "We are at last giving them hell."

Until 1971, when opium cultivation was banned under U.S. pressure, Turkey was one of the world's major growers of opium and principal sources of illicit heroin. According to then-president Richard Nixon, 80 percent of the heroin entering the United States illicitly every year was derived from the small opium fields in central Turkey.

In 1974, the cultivation of opium was resumed when the government gave in to pressure from impoverished opium farmers. However, the traditional method of "milking" the opium by the farmer was abandoned. Farmers instead were required to turn in the dried opium pod, which contains the milky opium, to the government soil products office.

This effectively dried Turkey up as a source of narcotics because the opium pod is not useful to smugglers. An expensive and sophisticated technique is required to obtain morphine or heroin from the pod.

"After Turkey stopped [being a source of heroin or morphine], Pakistan, Iran and Afghanistan exploded," the police officer said.

In the period 1970-1979, 1,760 tons of opium were harvested in these three countries, a total that would produce 176 tons of heroin.

"Addicts require three to four tons a year in the United States and a similar amount in Western Europe," the policeman said. So "just one year's harvest in these countries alone can keep the traffickers going for years," he added.

Underworld figures in Istanbul, with good conditions in Europe and the United States, took advantage of Turkey's situation as a land bridge between Asia and Europe and started regulating the westward flow of the drug.

The 286-mile Turkish-Iranian border is remote and mountainous.

"This has been an open border for thousands of years," and a region where "smuggling is an honored profession," the officer said. "You need a man every 50 yards to control it effectively."

Opium coming from the east was conveyed to laboratories in eastern Turkey in provinces such as Diyarbakir, Elazig and Van. It was then carried to Istanbul by car and thence to West Germany for distribution in Western Europe and to Italy and Sicily, where the "Italian Connection" seems to have come alive, for shipment to the United States.

"They try anything," said the police officer. "If you think they are watching cars they use trucks. If they think you are cracking down on trucks they use ships."

With overproduction in Iran, Pakistan and Afghanistan, where policing ranges from the nonexistent to the ineffective, there was an abundance of opium.

"In the old days when you seized 10 kilos [22 pounds] of heroin a gang would go broke," he said. "Now they can always go to the well for more."

This situation began to change after Gen. Kenan Evren, the chief of staff, seized power from Turkey's civilian government last September. For several years before the Army stepped in, Turkey was in chaos, with political terror beginning to erupt into civil war. The police force was politicized and impotent.

The Army seems to have reestablished law and order and the police force is becoming effective once more.

There is no addiction in Turkey.But the Ankara government has a strong interest in stopping the heroin trade: there are strong grounds to believe that the gangs are using the money they gain from narcotics trafficking to supply terrorists with weapons.

"We have seized enough arms to equip an army," Evren said recently, indicating the huge volume of the smuggling.

Another sign of the success of the Turkish narcotics police is the fact that many of the heroin laboratories in eastern Turkey have shut down. They have moved to western Iran, where, after the overthrow of the shah, there is virtually no law enforcement.

The police are now seizing more concentrated heroin that morphine base or opium, confirming that "heroin lab activity" in Turkey is diminishing as a consequence of the crackdown.

Another indication of the Turkish police's success is that trafficking seems to have started shifting from Turkey to Syria and Lebanon, where police are ineffective.

The United States, which has one of the worst drug addiction problems in the world, is giving Turkey $500,000 worth of training and equipment this year to reinforce Ankara in its battle against the Turkish drug "Mafia."