As part of NATO's adaptation to security challenges from the east and the south, the Alliance has opened eight Force Integration Units in Sofia (Bulgaria), Tallinn (Estonia), Riga (Latvia), Vilnius (Lithuania), Bydgoszcz (Poland) and Bucharest (Romania), Bratislava (Slovakia), and Székesfehérvár (Hungary). These small units represent a visible and persistent NATO presence in these member countries.

The primary mission of NFIUs is to foster collaboration between national forces and the NATO High Readiness Forces in times of military-political crises. Specifically, these small units provide broad planning support to facilitate the rapid deployment of Allied forces to the Eastern part of the Alliance and support collective defence planning. They also work with host nations to identify logistical networks, transportation routes and supporting infrastructure.

Each unit is manned by approximately 40 staff members, national as well as multinational NATO personnel, both on a rotational basis. As with all NATO assignments, the staff working at the NFIUs are paid by their respective nations. Construction and maintenance costs for the buildings are covered by the host nations. The NFIUs' expenses are partly covered through common funding by all 31 NATO Allies. This includes, for instance, the provision of collectively owned equipment such as computers and communication devices.

All of the NFIUs have undertaken challenging tasks since achieving full operating capability including, for those in the three Baltic States and Poland, assistance to the respective host receiving nations during the planning, deployment and integration of NATO's enhanced Forward Presence (eFP) in each of the countries.