The sound of drums, tanks, and thousands of goose-stepping soldiers echoed along this divided city's widest boulevard today as East Germany celebrated its 30th anniversary as a Communist state with its most impressive public display yet of military might.

With Soviet President Leonid Brezhnev and a host of other leaders from Soviet-bloc allies looking on, the East Germans paraded 24 new Soviet-built T72 tanks down "Karl Marx Allee." It was the first time this tank -- which is the latest and the main battle tank in the Soviet Army -- has been seen outside the Soviet Union's borders. East Germany is the only Warsaw Pact ally known to have it.

Yet, the parade seemed to have a strange, muted quality about it. The precision marching and military hardware that was supposed to project national strength could not entirely mask the insecurities of a state about the size of Ohio that still seals in its 17 million people behind fortified borders and the Berlin Wall.

At "Checkpoint Charlie," for example, the Western allies' crossing point into East Berlin, a small tank-like East German armored vehicle was parked just around the corner on a side street, apparently to block any driver in the parade who might try to make a dash for West Berlin.

The crowd along the parade route was officially estimated at about 10,000. There was little enthusiasm. Sporadic chanting appeared to have been rehearsed. Brezhnev, wrapped in a heavy coat and wearing a dark hat under the crisp, sunny skies, was helped up the stairs to the reviewing stand and sat with no sign of movement through the 35-minute parade.

The three World War II Western allies -- the United States, Britain and France-- filed a joint protest later in the day against the East German military display in the divided city which, under the postwar four-power agreement with the Soviet Union, is supposed to be a demilitarized.

Although East Germany boasts that it has done more to clear itself of the Nazi taint than the two-thirds of the country that is now West Germany, the events here this weekend left a number of Western observers with an eerie sense of the Hitler era, at least in the symbols of military might and political loyalty that were displayed.

Although the goose step is a traditional Prussian form of marching and is also found in other countries, it takes on a special quality when seen here. So do the perfect rous of young East German soldiers with gray uniforme and helmets, white gloves and automatic rifles, lined up facing their leader.

"The scene," noted a veteran Western diplomat, "resembles National Day, 1939."

Last night, an estimated 200,000 members of the Free German Youth held a torchlight parade along East Berlin's famed Unter den Linden boulevard, with spotlights and torchlight intermingling to produce an effect reminiscent of Nazi wartime rallies.

While the youths uere not in the Army, they all uore the same imitation-leather parkas.

The military show came just hours after Brezhnev, in a surprise announcement, pledged to withdraw unilaterally 20,000 of the roughly 400,000 Soviet troops in East Germany and 1,000 of the 7,000 Soviet tanks as a gesture of what he called good will toward detente. He coupled that, however, with a stern warning to Western European nations not to allow new U.S.-built intermediate-range missiles on their soil that could, for the first time, reach targets in the Soviet Union.