This task involves annotating the answer type to a given question that involve some kind of complex reasoning (including numerical reasoning). Note that the questions require looking at more than one part of the passage to answer. There are 3 possible answer types (i) spans, (ii) numbers and (iii) dates. If the answer can be found in the passage, label it as "span". If the answer is a number, label as "number". Similarly, label "date" if you think the answer to the given question is a date.

Passage: 1921 Persian coup d'etat, known in Iran as 3 Esfand coup d'etat , refers to several major events in Persia in 1921, which eventually led to the establishment of the Pahlavi dynasty as the ruling house of the country in 1925. The events began with a coup by the Persian Cossack Brigade headed by Reza Khan, and directed by the British, on 21 February 1921. With this coup Zia'eddin Tabatabaee took over power and became Prime Minister. The coup was largely bloodless and faced little resistance. With his expanded forces and the Cossack Brigade, Reza Khan launched successful military actions to eliminate separatist and dissident movements in Tabriz, Mashhad and the Janglis in Gilan. The campaign against Simko and the Kurds was less successful and lasted well into 1922, though eventually concluding with Persian success.
Question: What year did the Persions succeed with their coup d'etat?
date