Grycz-Śmiłowski was head of the Lutheran pastoral care service in Kraków. In 1934 he published A contemporary faith from the Holy Land ("Z ziemi świętej nowoczesne Wierzę") in which he presented himself as a free thinker, heir to the Polish Brethren. In 1936 he founded a small group started to publish the quarterly magazine Free Religious Thought ("Wolna Myśl Religijna"). In 1937 at a meeting in Łódź he founded the free religious association "Bracia Polscy", which in 1945 changed its name to "Jednota Braci Polskich".
Grycz-Śmiłowski aimed to follow the general outlines of the original Socinians, to proclaim the compatibility of faith with reason, and oppose the Trinity. They also practised baptism by immersion. Though how much detailed adherence there was to the original 1604 Racovian Catechism is open to question.
The Jednota continued in an uneasy stand-off with both the mainstream Protestant churches and the Communist Government after 1945. Shortly before Grycz-Śmiłowski's death in 1959 he was permitted to attend the 16th International Association for Liberal Christianity and Religious Freedom Congress in Chicago.
- Karol Grycz-Śmiłowski Bracia Polscy, Arianie - Unitarianie: zarys dziejów undated 16
- Karol Grycz-Śmiłowski Z ziemi świe̜tej nowoczesne "Wierze̜." 1937 - 51 pages
- Karol Grycz-Śmiłowski Wyganie i powrot Arian do Polski w 300-lecie ich męczeństwa 1934 262 pages
After Grycz-Śmiłowski's death in 1959
After the death of Grycz-Śmiłowskiego the Jednota evolved ideologically. It separated into two distinct groups: the Polish Brethren Unity Church of Unitarians in Krakow and Wroclaw, and the Panmonist group in Warsaw.
Jednota of Polish Brethren, Wroclaw
- In 1984 the main group joined the Pentecostals, while retaining certain elements of Arian belief. A feature of the Jednota is the attachment to the Law of Moses. They kept seventh-day Sabbath and celebrated the Lord's Supper on 14 Nissan, as well as keeping other Jewish holidays, such as the Feast of Tabernacles, and the Ten Commandments as recorded in the Pentateuch.
Panmonist Church, Warsaw
- The smaller group is the Zbór Panmonistyczny or Panmonist Church in Warsaw. Poland. Since 1997 this has joined the Polish Unitarian Church.
It is estimated that there are about 250 adherents in both groups.
- Charles A. Howe For faith and freedom: a short history of Unitarianism in Europe 1997 - 211
- Jahrbücher für Geschichte Osteuropas Osteuropa-Institut München - 2000
- The Christian leader / The Universalist leader 1937 "Mrs. Wilna Constable of Vancouver described the remarkable changes in the religious condition of the Philippine Islands where Archbishop Aglipay is leading the liberal Christian movement. Dr. K. Grycz-Smilowski represented Poland"
- I.A.R.F., Chicago, 1958: sixteenth congress, August 9–13, 1958, International Association for Liberal ... - 1959 "Reverend Karol Grycz-Smilowski, Krakow, Poland Reverend Karl-Ulrich Niedlich, Lunow, Kr. Eberswalde, DDR (Eastern Germany) Dr. Rudolf Kurschner, Berlin, Germany, for the Berlin Unitarian Church Reverend G. Bourquin, Berlin,
- Unitarian.org.uk Poland Archived 2011-07-20 at the Wayback Machine "In April 1997 the Polish Unitarian Church held its Founding Synod using a constitution registered with the Polish authorities in January 1997. This church is based in Warsaw, with some contacts elsewhere in Poland. It represents the merger of three post-World War I liberal religious strands: (a) a Panmonist (i.e. Universalist) group in Warsaw founded by Rev Marcin Lubecki; (b) a fellowship in Warsaw led by Rev Janusz Ostrowski but largely destroyed during the Second World War; and (c) the re-established Union of Polish Brethren started by Rev Karol Grycz-Smilowski in 1936. The latter suffered a takeover by Pentecostals who wanted a registered church organisation to get around their sect image so the Unitarians formed a new Union of Polish Brethren, Unitarian. This latter group is active today mainly in Silesia. The impetus for a merger and official registration came from wishing to avoid being considered a sect, which has real disadvantages under Polish law. Polish Unitarians are affiliated to the ICUU through the umbrella organisation, the Association of Unitarian Universalists in the Polish Republic."
- Religie.wiara.pl Jednota