The main source for ancient Greek diplomacy has been the writings of Thucydides. It is widely accepted that the first account of diplomacy at this period was a diplomatic conference held in 432 BCE. As Nicolson quoted from Thucydides, this conference was convened by Sparta to decide with its allies on punishing Athens with war due to its violation of treaties. While this conference was convened by Sparta for its allies of the Peloponnesian League against Athens, it is known that an Athenian delegation was also allowed to participate at and even to be involved in debates. In fact, the Athenian delegation was there for another specific mission but still was allowed to attend; and this is a sign that by 5th century BCE Greeks were aware of some diplomatic right and some kind of immunity.