On Nov. 4, 1979, Iranian students calling themselves the Muslim Student Followers of the Imam’s Line stormed the US Embassy in Tehran. The students claimed that with the 1953 coup in mind, they were worried that the United States would attempt to plot a coup against the Islamic revolution from within the embassy.

Ayatollah Ruhollah Khomeini, the leader of the revolution, expressed his support for the students, and 52 Americans were held hostage for 444 days. Relations between the United States and one of its greatest allies in the region at the time took a drastic turn, marking the start of 35 years of animosity and hostility.

Nov. 4, called simply by its Persian calendar date, Abaan 13, is an important day for the Islamic Republic and officials who insist that the United States must be perceived as Iran's number-one enemy. This year, however, Abaan 13 also fell on Ashoura, the day that Shiite Muslims commemorate the martyrdom of Hussein ibn Ali, the grandson of the Prophet Muhammad.

It is not clear why this year’s Abaan 13 ceremonies appeared subdued compared to previous years, even on social media. Fewer anti-US posters were shared on Facebook and Twitter than in previous years. One source in Iran told Al-Monitor on condition of anonymity that this year, Abaan 13 was overshadowed because it fell on the same day of Ashoura. Another source speculated that the nuclear negotiations led some officials to try to tone it down this year.