When talking about the Council of Trent, its important to understand the full history behind this council.
This was not a week or month long gathering of church officials; the council was first proposed in 1537
but it took until 1545 for the first sessions to begin. There were 25 sessions in total of which 8 were
overseen by Pope Paul III, 5 session by Pope Julius III and 12 session by Pope Pius IV. Notably, Pope Paul
IV did not hold any sessions during his tenure as papal head in the 1550s. While this was more typical for
past ecumenical councils, it means that the time period of Trent covers such a large period of Reformation
history. In contrast the Diet of Worms, where Luther initially defended his theological views in 1521, only
lasted from January to May. Many final decisions of the Council of Trent would be affected by historical
events that occurred throughout it, shifting Papal, secular & Protestant leadership and the growing divide
between Christian denominations in Europe.
When looking at the context of the council of Trent it is worth noting that it comes much later in the
Reformation (especially when considering the last sessions in which major responses were published).
Many early figures of the Reformation were dead or close to death before it had even ended in 1563;
most notably Martin Luther (died 1546), Martin Bucer (1551), John Bugenhagen (died 1558), Philip
Melcanchthon (died 1560) and John Calvin just after in 1564. So these major figures of the Reformation
did not participate and their responses to Trent were either preemptive or responding to small parts from
the council.
There are two main factors that affected Protestant participation in the Council of Trent. The first was
that despite many attempts by secular authorities and Protestant leaders the council remained a solidly
Catholic run affair. While Protestants were offered safe passage to the council, they were not given voting
privileges within this council. Thus from the get go, most Protestants were convinced that even if given
the chance to fully debate or articulate their views they would never be able to make any significant
changes.