Brussels — What is probably the strongest worldwide protest against the Polish military crackdown of the country's upstart workers has come from international unionists.
They have given considerable material and moral support in the past year to the emerging Solidarity labor organization.
During the first confused days of the martial law imposed by Gen. Wojciech Jaruzelski when most governments and international institutions adopted hesitant caution as their first reaction, the international labor movement headquartered here bristled with indignation.
Local and national unions instantly launched a wave of street demonstrations throughout Western Europe, sometimes in front of Polish embassies, against the official repression of their Polish counterparts in Solidarity.
The link between Poland's rank and file and their comrades in arms around the world was dramatically displayed here this week when a Solidarity leader, out of the country when martial law was imposed, addressed an international union strategy session on the crisis. He emotionally told the gathering of his organization's planned determination to wage a sustained campaign of nonviolent resistance.
The worldwide union outcry to martial law in Poland has been led by the International Confederation of Free Trade Unions (ICFTU) and the World Confederation of Labor, which represent independent unions with millions of members throughout the world, with the exception of the communist countries.
These organizations, headquartered here, have been intimately involved with Solidarity's emergence. Their officials have provided funds, advice, and equipment, such as printing presses, to Solidarity in the past 16 months.
And in the past few days, their leadership has been outspoken in their criticism of the Polish arrests of union members and also of Western governments for their repeated declarations that the matter was strictly an internal Polish affair.
In a television interview less than 24 hours after martial law was imposed in Poland, Jerzy Kulakowski, the general secretary of the World Confederation of Labor, commented that the Polish government's announced campaign against Solidarity leaders was a ''diversion.'' He said ''the repression is not just against extremists, but against the whole public.''
Just as rapidly, union leaders organized mass demonstrations in the streets of European capitals against the Polish action and called for Western pressure. ''This may galvanize Western European public opinion as much against the communist regimes as the antinuclear missile movement seemed directed against the Western alliance,'' observed one union staffer.
In a Dec. 16 evening strategy meeting on Poland, the ICFTU leadership called on Western governments to hold up food aid to Poland unless it was accompanied by outsiders or Polish church officials who could be trusted to ensure the supplies went to the public and not into official stores.
Such a position had been recommended by a Solidarity leader who had been in Western Europe when military rule was imposed and came to Brussels to address the meeting.
Stefan Trzynski, Solidarity's assistant spokesman for the Warsaw region, said that although the union's leadership had foreseen a crackdown and planned for it , ''we never expected a military state for the first time in Poland's history.''
He told journalists the Solidarity leadership had secretly prepared for a confrontation by stockpiling food, digging wells, and planning for alternative power in the factories they planned to occupy in case of such developments.''We can hold out for six months,'' he claimed.
He said that the arrests made early Sunday morning had missed a number of Solidarity leaders, but had also included a number of student and intellectual supporters. ''For every leader they arrest, 10 others will take their place, they can't put 10 million people in cages.''