I mean, I took this literally and just set my campaign in OD&D era (ce 1100s) Europe.
This was the original era (give-or-take) in real world history that corresponded to tech, military and social organization seen in D&D.
Just file off the names of real-world nations and replace them with my homebrew factions.
Peruse your Encyclopedia Britannica for a wealth of Eurocentric campaign hooks--
1106 AD Battle of Tinchebray- An English war of succession came to an end at the Battle of Tinchebray, in Normandy.
It began with the death of William II, King of England on August 2nd, 1100.
Henry I (Beauclerc) seized the throne, but was opposed by his brother Robert II (Curthhose), of Normandy.
Henry defeated Robert at Tinchebray and returned him in chains. Robert spent the rest of his life in prison.
1125 AD Henry V Dies Matilda Returns to England- Henry V, King of Germany and the Holy Roman Empire, died after leading an expedition against the French Louis VI.
His widow, Matilda, returned to England where her father forced English nobles to accept her as his successor after the death of his son at sea. When Henry I, her father, died Stephen of Blois, Henry's nephew, refused to accept Matilda's rule and he seized power. This resulted in a ten-year war of succession.
1147 AD Second Crusade - The Second Crusade was organized by Louis VII, King of Spain and Conrad III, King of Germany.
The Crusade came to a disastrous end due to a lack of leadership and control. It ended with an aborted siege of Damascus.
1147 AD Morrocco Conquered By Almohads - Morocco was conquered by Abd al-Mumin, the leader of the Berber Muslim Almohad Dynasty.
This conquest brought to an end the Almoravid Dynasty. By 1152, Algeria was also brought under the control of the Almohads.
1157 AD Eric IX Jedvardsson Defeats Finns- Eric IX (Jedvardsson) Christian King of Sweden, defeated the Finns.
He then forced them to convert to Christianity.
1163 AD Work Began On Notre Dame- One of the most notable gothic churches was begun in 1163- Notre Dame.
The church was conceived by Maurice de Sully, bishop of Paris.
1168 AD Oxford Founded- The school of Oxford was founded in 1168. After the founding of the University of Paris in 1200 Oxford became an offshoot of it.
1171 AD Saladin Founds Ayyubid Dynasty- Saladin, ruler of Egypt, proclaimed the end of the Fatima dynasty that had ruled Egypt since 968.
He declared himself Caliph of the new Ayyubid dynasty.
1171 AD Henry II Launches Invasion of Ireland- Henry II, King of England responded to a request for help from Ireland's deposed King Dermot MacMurrough, by sending forces to Warford.
Henry was recognized as the ruler of Ireland by the Treaty of Windsor in 1171.
1174 AD William The Lion Defeated- Henry II defeated William the Lion, King of Scotland at the siege of Alnwick Castle in 1174.
William officially accepted Henry as the ruler of Scotland.
1176 AD Frederick I Barbarossa Defeated By Lombard League- The Holy Roman Emperor, Frederick I (Barbossa) was decisively defeated by the Lombard League at Legano. Frederick was attempting to reassert his authority over northern Italy.
1184 AD Streets Paved In Paris- The streets in front of the Louvre were paved. This marked the first time streets in Paris were paved.
1187 AD Battle Of Hittin- Christian forces from the Kingdom of Jerusalem attacked a caravan carrying the sister of Saladin.
In retaliation, he began a holy war against the Crusaders. At the Battle of Hittim, he defeated a combined Christian army.
He then laid siege to Jerusalem and captured it, although he did not sack the city after the conquest.
1186 AD Second Bulgarian Empire- A successful revolt took place against the Byzantine rule of Bulgaria.
This established the second Bulgarian empire which lasted until 1396.
1192 Ad Crusader Captures Acre- Spurred by Saladin's triumph, the Christians launch the Third Crusade, led by Richard the Lionhearted.
Despite many difficulties, they reached the coastal area of the Holy Land and successfully captured the Acre fortress.
Richard negotiated a truce with Saladin that ensured Christian access to holy sites in Jerusalem.
1199 AD Richard The Lionhearted Dies- Richard the Lionhearted died of an arrow wound while besieging Chalus in Western France.
Richard, ruler of England since 1189, had actually spent very little time there. Instead, he helped lead the Third Crusade.
Richard had been imprisoned by the Holy Roman Emperor in 1193, but managed to purchase his freedom.
He fought an on-going battle with Philip II of Normandy.
While Richard was involved in affairs outside England, the land was administered for him by Jubert Walter
