The SIPRI Yearbook is an authoritative and independent source of data and analysis on armaments, disarmament and international security. It provides an overview of developments in international security, military expenditure, weapons and technology, arms production and the arms trade, armed conflict and conflict management, and efforts to control conventional, nuclear, chemical and biological weapons.This 53rd edition of the SIPRI Yearbook covers developments during 2021, including:US BLArmed conflict and conflict management, with an overview of armed conflict and peace processes across the Americas, Asia and Oceania, Europe, the Middle East and North Africa, and sub-Saharan Africa, as well as a focus on global and regional trends in peace operationsBE UE US BLMilitary expenditure, international arms transfers and developments in arms productionBE UE US BLWorld nuclear forces, with an overview of each of the nine nuclear-armed states and their nuclear modernization programmesBE UE US BLNuclear arms control, featuring developments in the Russian-United States strategic dialogue, Iran''s nuclear deal and the multilateral nuclear arms control and disarmament treaties, including the entry into force of the Treaty on the Prohibition of Nuclear WeaponsBE UE US BLChemical, biological and health security threats, including the impact of the Covid-19 pandemic, the investigation of allegations of chemical weapon use in Syria and developments in the international legal instruments against chemical and biological warfare BE UE US BLConventional arms control and regulation of new weapon technologies, with a focus on inhumane weapons and other conventional weapons of humanitarian concern, including efforts to regulate autonomous weapon systems, state behaviour in cyberspace and space, and developments in the Open Skies TreatyBE UE US BLDual use and arms trade controls, including developments in the Arms Trade Treaty, multilateral arms embargoes and export control regimes, and review processes in the legal framework of the European Union for such controls as well as annexes listing arms control and disarmament agreements, international security cooperation bodies, and key events in 2021.BE UE