Al-Fatah (The Victory)
Surah 48 · Verse 18
Allah was indeed pleased with the believers when they swore allegiance {2} to you under the tree, and He knew that which was in their hearts so He sent down tranquility on them and rewarded them with a near victory,
These verses refer to Treaty of Hudibiya and the campaign of Khaiber.
Campaign of Khaiber (H 7):
Khaiber was the stronghold of Jewish tribes; where all enemies of muslims had gathered and organised themselves for a war. The prophet (PBH) led a campaign against Khaiber, conquered the fort and made the Jews surrender.



