U.S. security sector assistance to foreign countries is funded primarily in the foreign affairs and defense budgets. As the 115 th Congress considers its spending priorities for the coming fiscal year, the magnitude, trends, and uses of such assistance may be examined and debated. The Department of State, Foreign Operations, and Related Programs (SFOPS) appropriations; the National Defense Authorization Act (NDAA); and the Department of Defense (DOD) appropriations all contain provisions that could affect security assistance funding in FY2018 and beyond. While the Department of State (DOS) and the Department of Defense (DOD) are the primary actors in the provision of such assistance to foreign countries—and the primary focus of this CRS report―other U.S. agencies may also conduct related programs, including the U.S. Agency for International Development (USAID); the Departments of Energy (DOE), Homeland Security (DHS), Justice (DOJ), and the Treasury; and parts of the intelligence community. With the Foreign Assistance Act of 1961 (FAA, P.L. 87-195) and later the Arms Export Control Act of 1976 (AECA, P.L. 90-629), as amended, Congress established the foundational authorities for contemporary U.S. security assistance programs. These authorities charged the Secretary of State with responsibility to provide "continuous supervision and general direction" of foreign assistance and contained specific reference to "military assistance, including military education and training," to ensure its coherence with foreign policy. Over time, the Secretary of State's security assistance authorities expanded to include international narcotics control, peacekeeping operations, antiterrorism assistance, and nonproliferation and export control assistance. The State Department's authorities were codified in Title 22 of the U.S. Code (Foreign Relations and Intercourse), and funds for such assistance programs are largely appropriated through State Department accounts. Such assistance to foreign governments, security forces, and militaries covers a wide spectrum of activities, including the transfer of conventional arms, training and equipping regular and irregular forces for combat, law enforcement training, defense institution reform, humanitarian assistance, and engagement and educational activities. These activities may serve multiple purposes for both the United States and the recipient country. DOD has long played a crucial role in the implementation of Title 22 security assistance programs and activities, but for many decades, it otherwise relegated the training, equipping, and assisting of foreign military forces as a secondary mission on its list of priorities, far below war-fighting. Beginning in the 1980s, Congress began providing DOD with additional authority in Title 10 of the U.S. Code and annual NDAAs to conduct a range of programs and activities funded by DOD appropriations. Congress began providing such authorities in the 1980s for counternarcotics and humanitarian assistance; authority for nonproliferation and counterterrorism programs was subsequently added in the 1980s and 1990s. In recent years, the international security environment, and the associated perceived threats to the United States homeland, has led DOD increasingly to give greater priority to building and strengthening security partnerships in a variety of contexts around the world. Particularly since the terrorist attacks of September 11, 2001, Congress has granted DOD new authorities in annual NDAAs and in Title 10 (Armed Services) of the U.S. Code to engage in "security cooperation" with foreign militaries and other security forces—now considered by DOD to be an "important tool" for executing its national security responsibilities and "an integral element of the DOD mission." This trend underlies a significant expansion of DOD direct engagements with foreign security forces and an accompanying increase in DOD's role in foreign policy decisionmaking. As the United States undertook military action and increased the scope of its foreign counterterrorism operations, Congress provided a number of DOD crisis and wartime authorities, some providing new global authority and some specific to certain geographic areas. In enacting these new authorities and appropriations, Congress has bolstered an expanding global DOD role in building foreign partner capacity through programs to train and equip foreign security forces, notably in the realms of counterterrorism, counternarcotics, and defense institution building. In addition, DOD is authorized to carry out various security cooperation and logistical support activities, as well as advise and assist missions that may have the added impact of boosting partner country capabilities. DOD's security cooperation authorities were most recently and significantly modified in the FY2017 National Defense Authorization Act (NDAA) ( P.L. 114-328 ; signed December 23, 2016), which enacted several new provisions that modify the budgeting, execution, administration, and evaluation of DOD security cooperation programs and activities. Implementation of these provisions remains a work in progress. The expansion of DOD's engagement with foreign partner militaries over the past decade has both policy and budgetary implications. These include the overall size and scope of U.S. security assistance activities worldwide, the geographic distribution of such activities, and the relative influence of DOS and DOD in interagency security policymaking processes. Another implication relates to congressional committees of jurisdiction, as primary oversight and funding prerogatives have progressively extended and migrated from foreign relations to defense authorizers and appropriators. Yet, challenges continue to exist in the development of consistent interagency action and terminology to describe the range of security assistance and cooperation programs and activities funded by the U.S. government. Moreover, funding data for security assistance and data on historical security assistance funding are incomplete. Although DOS has long been required to track most security assistance funding by aid account and on an individual country basis, DOD has not. As a result, comparisons between security assistance funding provided by both departments are challenging, and totaling the two may leave gaps. The 115 th Congress is continuing scrutiny and debate on security assistance matters. Within the Department of State, Foreign Operations, and Related Programs FY2018 budget request, the Administration is seeking to reduce international security assistance by about $2.3 billion, or 24.4%. Each of the security assistance programs would be reduced by amounts ranging from 9% to more than 54%. In addition, the Administration proposes making changes to security assistance programs, such as designating 95% of the Foreign Military Financing (FMF) program to four countries. The remaining 5% of the funds, rather than being made available on a grant basis globally as FMF is currently implemented, would be made available to all other countries with a combination of grant and loan assistance to be coordinated with DOD. Congress is also debating a possible increase of Overseas Contingency Operations (OCO) funds for defense and nondefense, including for funding security assistance activities in FY2018. Currently, there is no DOD budget request for security cooperation programs and activities that is comparable to the Department of State, Foreign Operations, and Related Programs FY2018 budget request for State Department-managed security assistance accounts. Soon, however, this may change; Section 1249 of the FY2017 NDAA added a new section to Title 10 of the U.S. Code , requiring the President, beginning with the FY2019 budget, to submit a formal, consolidated budget request for all DOD's security cooperation efforts, including the military departments and, as practicable, by country or region and by authority. For further background on U.S. security assistance and cooperation policies, see CRS Report R44444, Security Assistance and Cooperation: Shared Responsibility of the Departments of State and Defense ; CRS Report R44602, DOD Security Cooperation: An Overview of Authorities and Issues ; CRS Report R44313, What Is "Building Partner Capacity?" Issues for Congress ; and CRS In Focus IF10582, Security Cooperation Issues: FY2017 NDAA Outcomes . Based on DOS and DOD funding data, the U.S. government has provided at least $204.6 billion to provide security assistance and cooperation to allied countries abroad between FY2006 and FY2016. In that timeframe, DOD funded approximately $115.4 billion in security cooperation activities worldwide, averaging $10.5 billion annually, while the State Department funded approximately $89.2 billion in security assistance worldwide, averaging $8.1 billion annually. Overall funding peaked in FY2011, when a total of $21.6 billion was obligated, largely due to the surge in support activities in Afghanistan. Security assistance funding managed by DOS peaked at $9.4 billion in FY2015 because of increased funds to counter the Islamic State terrorist organization and security aid to the Middle East. For DOD, funding peaked at $12.8 billion in FY2008, with funding increases for Afghanistan and Iraq security. After adjusting for inflation, the constant dollar total trend line illustrates the same peaks and troughs as the current dollar trend. However, it illustrates a general decline overall in recent years as compared with the funding levels of earlier years―FY2006-FY2012 funding levels (see Figure 1 ). In the past decade, DOD has typically obligated a larger portion of overall security cooperation funding compared to DOS, though State obligated nearly half of U.S. security assistance funding in FY2013, FY2014, and FY2016. The highest share of DOD obligations occurred in FY2007 (61%) and FY2008 (63%). (See Figure 2 below.) In FY2016 (the most recent year for which complete country allocations are available), the top 10 recipients of U.S. security assistance and cooperation accounted for $7.8 billion (45%) of the combined funding provided by DOS and DOD for that year. Figure 3 illustrates the dollar amount and share of the top 10 recipients of U.S. security assistance and cooperation. Of the $7.8 billion that went to the top 10 recipients in FY2016, Israel had the largest share at 40%, followed by Egypt at 17%, Afghanistan at 10%, and Iraq at 9%. Combined, Israel and Egypt received 57% of the top 10 share.