Roland Jahn arrived in West Germany by train last week, deprived of his East German citizenship - the latest example of the seriousness with which communist officials view the growing peace movements within the East bloc.
Mr. Jahn was the 20th member of the peace movement in the East German town of Jena to be so expelled to the West. He said he had been pressured into applying for a visa to leave East Germany and forced onto a train by security forces.
Once scorned by Western officials and activists as mere propaganda appendages of their manipulative governments, some communist-bloc peace and antinuclear protesters now are seen as an increasingly independent force. And they are beginning to attract public support.
In recent weeks, a West European government has prepared an internal document detailing this growing phenomenon in the Soviet bloc. A leading Western peace and disarmament publication has given it wide coverage. And last month a number of prominent members of the West German Green Party demonstrated on Alexanderplatz, East Berlin's main square, before they were detained and ousted by the police there.
Western contacts and attitudes toward the official and unofficial movements in the East have sometimes been ambiguous. Some Western protest groups and activists want nothing to do with the official communist peace organs, such as the Moscow-sponsored World Peace Council, which is holding ''a world assembly for peace and life against nuclear war'' June 21 to 26 in Prague. Most Western activists prefer to deal with the independent Eastern groups.
Attempts to cooperate with and assist genuine peace and antinuclear movements in the East were a strategy advocated two years ago by British activist E.P. Thompson and others in the European antinuclear movement to establish a better image of neutrality and balance.
A recent West European government's survey of activities in the Soviet Union, East Germany, Hungary, and Czechoslovakia noted that ''a number of apparently independent peace movements have begun to make their voices heard - only to be harassed in most cases by the authorities because they challenge East as well as West on the arms race.''
Both the government survey and a Dutch-based disarmament publication remarked that the Soviet independent Group for Establishing Trust Between the USSR and USA has emphatically denied that it is ''dissident'' and has sought to work entirely within Soviet law. It advocates mutual disarmament, encounters between the children of Soviet and American leaders, and televised discussions in both countries. Some 900 people signed an appeal in Moscow in early 1983, and similar autonomous groups have sprung up in Leningrad, Odessa, and Novosibirsk.
Most of the original leaders have been detained, placed under virtual house arrest, told to leave the country, or branded as ''renegades and criminals,'' according to these reports. An artist, Sergei Batovrin, the son of a Soviet diplomat, was held for a month in a Moscow mental hospital, went on a hunger strike, and was recently granted an exit visa with his family.
The government survey also notes that a number of official Soviet publications and speeches have ''revealed concern at the growth of antimilitarist sentiments among young people.''
Both studies also outlined the growing church and other activity in East Germany. These activities were tolerated in 1981 and 1982 but finally led to the crackdown and expulsions within the past few months.
The movement was originally condoned by the East German authorities. But it increasingly became a forum against the militarization of the country and for advocating the withdrawal of foreign troops and nuclear weapons from both East and West Germany.
The eventual banning of badges distributed by churches was widely noted. The badges depicted the beating of swords into plowshares in a design based on a Soviet sculpture given by the Soviet Union to the United Nations. The sculpture bears the same slogan as the West German peace movement: ''Make peace without weapons.''
Mass meetings, workshops, and church declarations continued. Sometimes the meetings drew thousands of participants. The repression followed.
The broadening involvement of East German churches in this movement ''could make life difficult for the authorities if it snowballed,'' a European activist noted.
Religious and student activists were at the base of the movement in Hungary, which has also been tolerated by the government. The most prominent has been the Peace Group for Dialogue, which has issued statements asking: ''If the Dutch can demonstrate against American missiles, why can't we demonstrate against Soviet missiles?'' There have been indications that the authorities might be moving to compromise or take over this movement.
Although these reports have devoted less space to them, there are bilateral disarmament demands in officially sanctioned activities in Romania, the Solidarity trade union movement in Poland, and the Charter 77 human rights group in Czechoslovakia.
A comment in the disarmament publication on the subject noted in both East and Western Europe that ''there is a new campaign of 'detente from below'. . . . It is hoped that one of the legacies of this peace movement will be that the future of Europe was decided by popular pressure so strong that it was impossible for politicians to ignore it.''