The IUN also manages a peacekeeping military known as the International United Nations Peacekeeping Force (IUN-PKF or IUN PKF), more commonly referred to as the International Union Peacekeeping Force (IUPF).
By 1996, the IUN was involved in peacekeeping efforts during a standoff between FCU and Erusean forces in Ugellas and Amber. However, the FCU forces retreated on April 20, 1996 following the Ulysses 1994XF04 announcement; their retreat forced the IUN to also retreat. The IUN's retreat was notably hampered by logistical difficulties and heavy storms, preventing their retreat from fully taking place until April 22.
Sometime following the Continental War, a group of Erusean rebels seized a military factory that was under the IUN's control. The rebels, calling themselves Free Erusea, launched attacks across the Usean continent. The Independent State Allied Forces launched Operation Katina to quell the rebellion.
In 2019, the IUN attempted to quell hostilities between the Osean Federation and Erusea. During the ensuing Lighthouse War, the IUN-PKF assisted Osean forces in pushing Erusean forces back towards the country's borders. Part of this effort included sending AWACS Sky Keeper to assist the Osean Air Defense Force squadrons stationed at Fort Grays Island.
- The IUN plays a similar role to the United Nations in the real world.
- The Neo United Nations played a similar peacekeeping role in Ace Combat 3: Electrosphere. Since the IUN was introduced in Ace Combat 04 promotional material, it may have acted as a retcon for the Neo United Nations.
- VR Mission 01, Ace Combat 7: Skies Unknown.
- Charge the Enemy, Ace Combat 7: Skies Unknown.
- Two-pronged Strategy, Ace Combat 7: Skies Unknown.
- "Charge Assault", Ace Combat 7: Skies Unknown
- Usea Today: Asteroid on Collision Course With Earth!
- ISAF Bulletin.
- Arcade Mode, Ace Combat 5: The Unsung War.
- File:Ace Combat 7 Skies Unknown - PGW 2017 PS VR.
- File:Ace Combat 7 Skies Unknown - PS4 VR Gameplay Trailer
- ［TGS 2018］「エースコンバット7」VRモードの詳細を主要開発スタッフに聞く。「サマーレッスン」チームが挑んだ“本物のパイロット体験”とは