The SIPRI Military Expenditure Database contains consistent time series on the military spending of countries for the period 1949–2018.

From the Bonn International Center for Conversion: The GMI compares a country’s military expenditure with its Gross Domestic Product (GDP) and its health expenditure.

Measures regime characteristics (democracy/autocracy) for all states over 500,000 from 1800 to 2008.

List of sources for data on global conflict and security. Many require you to register to download data. Variety of interfaces can be difficult to navigate, so reach out if you need help. *Some links are not available without a Princeton login.*

An open repository hosted at Harvard in which authors can deposit their replication datasets. Includes datasets from important journals and research projects, such as American Journal of Political Science and survey organizations like Gallup.

Armed Conflict and Intervention (ACI) Datasets: Forcibly Displaced Populations; Major Episodes of Political Violence; PITF State Failure Problem Set; High Casualty Terrorist Bombings and more.

The Armed Conflict Location & Event Data Project (ACLED) is a disaggregated data collection, analysis, and crisis mapping project. ACLED collects the dates, actors, locations, fatalities, and types of all reported political violence and protest events across Africa, East Asia, South Asia, Southeast Asia, the Middle East, Central Asia and the Caucasus, Latin America and the Caribbean, and Southeastern and Eastern Europe and the Balkans. T

Report and Map of countries in which the U.S. government conducted operations it explicitly described as counterterrorism, in an outgrowth of President George W. Bush's “Global War on Terror.” These operations include air and drone strikes, on-the-ground combat, so-called “Section 127e” programs in which U.S. special operations forces plan and control partner force missions, military exercises in preparation for or as part of counterterrorism missions, and operations to train and assist foreign forces.

The Costs of War Project is a nonpartisan research project based at the Watson Institute for International and Public Affairs at Brown University that seeks to document the direct and indirect human and financial costs of U.S. wars in Iraq and Afghanistan and related counterterrorism efforts.

Tracking the United States’s Drone Strikes and Other Operations in Pakistan, Yemen, Somalia, and Libya

Article from Perspectives on Terrorism listing and describing a number of databases and data sets on the GWOT.

From Tufts Center for Strategic Studies, creating a omprehensive dataset of all US military interventions from 1776 until 2017 to measure the costs, benefits, and unintended consequences of US military involvements abroad.