Yemen's civil war escalated dramatically in March 2015 when a Saudi-led coalition intervened against the Houthi movement, which had seized the capital Sana'a. UN OCHA estimated 233,000 deaths by 2020, with 131,000 from indirect causes such as famine and disease. The UNDP projected 377,000 total deaths by end of 2021. Yemen became the world's worst humanitarian crisis, with 21 million people requiring aid. A UN-brokered ceasefire held from April 2022; Houthi attacks on Red Sea shipping from late 2023 drew U.S. and UK strikes.