Nothing better illustrates the Eritrean revoluntionaries' growing strength and military sophisticated in their long war of independence against Ethiopia than their classic siege and recently claimed capture of Nakfa.

From a military viewpoint, the operation was a small-scale, poor man's Dienbienphu, with troops of the Eritrean People's Liberation Front holding the surrounding mountains and nibbling away at the Ethiopian garrison in a six-month siege.

In more recent actions, the Eritreans have reported the capture of Edd, a town on the Red Sea coast, and Tuesday on the Sudanese border.

But after 16 years of fighting the Ethiopian army, trained and armed by the United States, the Eritreans have few illusions about Ethiopian willingness to negotiate an overall settlement as France did in Indochina after Dienbienphu's fall in 1954.

They are convinced that Ethiopia under the Marxist military regime called the Dergue is no more able to accept Eritrean independence than was the late Emperior Haile Selassie, who was overthrown in 1974.

But following the capture of Kerora on the Sudanese border mear the Red Sea in January, the victory at Nakfa for the first time cleared one of Eritrea's nine districts - the Sahel - of any government military presence.

That should allow the revolutionaries to bring greater pressure to bear on the half dozen remaining Ethiopian military strongholds. The most likely next target is Keren, a highlands city where more than a fifth of the Ethiopian army's expeditionary force of about 24,000 is located.

The plight of the Ethiopians - bottled up in their strongholds except for an occasional foray outside in armored convoys - is symbolized by the fact that they are outnumbered by the Eritreans, instead of having the classic counterinsurgery edge in manpower, which ranges from 4 to 1 to 10 to 1.

Over the past two years the Eritreans - both the EPLF and the larger Eritrean Liberation Front - have gone on the offensive after years of hit-and-run guerrilla warfare Smaller Ethiopian garrisons have fallen to the Eritreans with increasing regularity over-the past 18 months.

But the Nakfa operation reflected their ability to mount a complicated siege and fight off three Ethiopian relief efforts - including two parachute drops and an armor-backed, 5,400 man road opening action.

For months before the siege began in September 1976, thousands of EPLF troops hacked an all-weather road from the mountains to provide unimpeded logistics support for the operation.

Other rudimentary roads crisscross Eritrea while the Ethiopians find it next to impossible to use the old roads, which the Eritreans have interdicted by blowing up bridges.

Once the siege began, the 700-man Nakfa garrison was dependent on weekly airdrops of supplies from a fighter-protected C-199 flying boxcar. But many of the parachutes fell into Eritrean hands. The several thousand Eritreans hands. The Nakfa were in no hurry. They patiently invested the town, whose more than 15,000 residents fled to safety, and removed 900 Ethopian-laid landmines.

A week before its reported capture, Nakfa looked like a ghost town. The 200 or so Ethiopian troops who had survived the siege - many others had been picked off by the Eritreans as they sought to collect the air drops in broad daylight - were living in underground bunkers in two of the three remaining strongholds.

But with Eritreans tunneling only 200 feet from the main camp, Eritrean commanders predicted - apparently accurately - that victory would be theirs within a few days.

Even the Ethiopian air force seemed to have written off the garrison, for there had been no resupply flight for 18 days. The previous flight had touched off furious radio conversations between the trapped troops and the transport plane's pilot. The foot soldiers cursed the pilot's refusal to fly low enough for accurate parachute drops. And through him they sent their final messages to wives and children.

Precise planning and caution had more than made for the lack of sophisticated weapons. The Eritreans rely almost entirely on American equipment captured from the Ethiopians - ranging from World War II carbines and M-1s, to M14s and 81-MM, mortars. Soviet heavy machine guns, used as antiaircraft weapons, have bagged 15 fixed-wing aircraft and helicopters during the Nakfa siege, the Eritreans claimed.

But they make no secret of their desire to obtain heavy artillery - captured American-made 106-mm, recoilless rifles are the biggest weapon now in their inventory - and shoulder-held Soviet-made antiaircraft missiles. The artillery would prove useful in harassing pinned-down Ethiopian garrisons. And the SAMs would help neutralize the Ethiopian air force's Korean War-vintage F-86 fighters and C-19 transports and more modern F-5E ground-support jets.

But the Eritreans seem much has upset by Ethiopian airpower than they were several years ago. Thanks to a system of Japanese walkie-talkies linked to forward observers near the Ethiopian air force base at Asmara, their units throughout Eritrea are tipped off immediately about enemy sorties. The Asmara air base, like the Eritrean capital city itself, is said to be so insecure after dark that the Ethiopians do not leave their planes there overnight, but prefer to fly them back 500 miles to air force headquarters at Debre near Addis Ababa.

Soldiers near Nakfa have grown so accustomed to the different pitches of various aircraft engines that despite the low cloud cover they only smiled when suddenly the unmistakable roar of a jet was heard. "Passenger plane on its way north to Khartoum and Cairo," a young soldier said laughingly.

Although refugees in the Eritrean-controlled areas still carefully sweep away tracks left in the desert by guerrilla car movements for fear of air raids, the guerrillas themselves increasingly violate their once-ironclad prohibition against daylight traveling.

Such self-confidence was reflected by the two young EPLF Politburo members who had arrived from headquarters to oversee the final siege operations.

A visitor jokingly suggested that President Carter was making a mistake in cutting back on arms deliveries to Ethiopia, since the guerrillas seemed to be taking massive delivery of everything from ponchos to army trucks.

"Still we would prefer to have the Americans stop. This is a step-by-step conflict, a people's war.We are like ants. Why do you Americans try to stop us?"