over-heavy burdens laced upon them, he wrote, they must be especially protected since the rich and powerful have many other means to protect their interests. The state, he argued, must legislate to protect workers from low pay, over-long working hours or over-taxing work and avail themselves of the protection provided by membership of trade unions. Reaction to the encyclical The encyclical was followed in areas of Italy with the creation of social movements that expressed and campaigned for the alleviation of social concerns in local areas. Members of the church supported and became involved in campaigns in support of working people including contributions of personal money for those causes. The plight of cotton workers was an example of such causes and financial and moral support for a strike that started on 22 September 1909 in Bergamo (known as he "fifty day strike") was provided by local bishop Giacomo Maria Radini-Tedeschi and Father Angelo Roncalli (future Pope John XXIII) who saw in it the need for "pastoral modernity" in the Church. Such support for social movements became unpopular, however, when Pope Pius X replaced Leo in 1903. Catholic involvement in Italian political life had been banned under previous popes and Pius allowed a network of spies to operate which identified and reported on the support for social and political movements and subjected them to questions, apostolic visits and pressure to desist. Rerum novarum dealt with persons, systems and structures, the three co-ordinates of the modern promotion of justice and peace, now established as integral to the church's mission. In the years which followed there have been numerous encyclicals and messages on social issues; various forms of Catholic action developed in different parts of the world; and social ethics taught in schools and seminaries. To mark the 40th anniversary of Rerum novarum, Pope Pius XI issued Quadragesimo anno, which expanded on some of its themes. Pope John XXIII Further development came in the post–Second World War period when attention turned to the problems of social and economic development and international relations. On 15 May 1961 Pope John XXIII released Mater et magistra, subtitled "Christianity and Social Progress". This encyclical expanded the church's social doctrine to cover the relations between rich and poor nations, examining the obligation of rich countries to assist poor countries while respecting their particular cultures. It includes an examination of the threat of global economic imbalances to world peace.