The Treaty of Nymphaeum was a peace treaty

Peace treaty

A peace treaty is an agreement between two or more hostile parties, usually countries or governments, that formally ends a state of war between the parties...

 signed in December of 1214 between the Nicaean Empire, successor state of the Byzantine Empire

Byzantine Empire

The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...

, and the Latin Empire

Latin Empire

The Latin Empire or Latin Empire of Constantinople is the name given by historians to the feudal Crusader state founded by the leaders of the Fourth Crusade on lands captured from the Byzantine Empire. It was established after the capture of Constantinople in 1204 and lasted until 1261...

, which was established in the aftermath of the Fourth Crusade

Fourth Crusade

The Fourth Crusade was originally intended to conquer Muslim-controlled Jerusalem by means of an invasion through Egypt. Instead, in April 1204, the Crusaders of Western Europe invaded and conquered the Christian city of Constantinople, capital of the Eastern Roman Empire...

 of 1204.

Background

Following the Fourth Crusade, Baldwin IX of Flanders was elected emperor of the Latin Empire and was recognized to have not only a portion of Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

 (the remainder was given to the Venetians

Republic of Venice

The Republic of Venice or Venetian Republic was a state originating from the city of Venice in Northeastern Italy. It existed for over a millennium, from the late 7th century until 1797. It was formally known as the Most Serene Republic of Venice and is often referred to as La Serenissima, in...

), but also the north-west region of Asia Minor

Asia Minor

Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

, although recognition of sovereignty did not mean actual control of the territory. It was up to the emperor to exercise that control, by force of arms if necessary. Following the Fourth Crusade, Baldwin was occupied with events in Thrace

Thrace

Thrace is a historical and geographic area in southeast Europe. As a geographical concept, Thrace designates a region bounded by the Balkan Mountains on the north, Rhodope Mountains and the Aegean Sea on the south, and by the Black Sea and the Sea of Marmara on the east...

 and was later taken prisoner by the Bulgarians

Bulgarians

The Bulgarians are a South Slavic nation and ethnic group native to Bulgaria and neighbouring regions. Emigration has resulted in immigrant communities in a number of other countries.-History and ethnogenesis:...

 in the Battle of Adrianople

Battle of Adrianople (1205)

The Battle of Adrianople occurred on April 14, 1205 between Bulgarians under Tsar Kaloyan of Bulgaria, and Crusaders under Baldwin I. It was won by the Bulgarians after a skillful ambush using the help of their Cuman and Greek allies. Around 300 knights were killed, including Louis of Blois, Duke...

 in April of 1205. Asia Minor was ignored by the Latins for the time being, thus giving a breathing space for Theodore Lascaris, who had declared himself emperor and was based at Nicaea

Nicaea

Nicaea or Nikaia may be:*The ancient name of several places, including:** İznik, Turkey - formerly Nicaea capital of the Empire of Nicaea**Nice, France**Nicaea, Locris, a fortress city of the Locri Epicnemidii...

, to consolidate his power and focus his attention on the Sultanate of Rûm

Sultanate of Rûm

The Sultanate of Rum , also known as the Anatolian Seljuk State , was a Turkic state centered in in Anatolia, with capitals first at İznik and then at Konya. Since the court of the sultanate was highly mobile, cities like Kayseri and Sivas also functioned at times as capitals...

 during this time.

Baldwin's brother, Henry

Henry of Flanders

Henry was the second emperor of the Latin Empire of Constantinople. He was a younger son of Baldwin V, Count of Hainaut , and Margaret I of Flanders, sister of Philip of Alsace, count of Flanders....

, took over the Latin Empire and started operations against the Nicaean Empire at the end of 1206, but these were only minor engagements until Henry focused his attention in 1211. On October 15 of that year, Henry won a major victory at the Battle of Rhyndacus River and pushed forward onto Pergamum and Nymphaeum, but guerrilla warfare on Theodore's part limited Henry's further advances. Due to both sides being exhausted, the Treaty of Nymphaeum was signed between the two emperors, halting the Latin advance into Asia Minor. The Latin holdings were confined to the north-western part of Anatolia, comprising the coasts of Bithynia

Bithynia

Bithynia was an ancient region, kingdom and Roman province in the northwest of Asia Minor, adjoining the Propontis, the Thracian Bosporus and the Euxine .-Description:...

 and most of Mysia

Mysia

Mysia was a region in the northwest of ancient Asia Minor or Anatolia . It was located on the south coast of the Sea of Marmara. It was bounded by Bithynia on the east, Phrygia on the southeast, Lydia on the south, Aeolis on the southwest, Troad on the west and by the Propontis on the north...

.

Aftermath

Although both sides would continue to fight for years to come, there were some important consequences of this peace agreement. First, the peace treaty effectively recognized both parties, as neither one was strong enough to destroy the other. The second consequence of the treaty was that David Komnenos

David Komnenos

David Komnenos was one of the founders of the Empire of Trebizond and its joint ruler together with his brother Alexios until his death.-Early life:...

, who had been a vassal of Henry and who had been carrying out his own war against Nicaea with the support of the Latin Empire, now effectively lost that support. Theodore was thus able to annex all of David's lands west of Sinope

Sinope

Sinope may refer to:*Sinop, Turkey, a city on the Black Sea, historically known as Sinope** Battle of Sinop, 1853 naval battle in the Sinop port*Sinope , in Greek mythology, daughter of Asopus*Sinope , a moon of the planet Jupiter...

 in late 1214, gaining access to the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

. The third consequence was that Theodore was now free to wage war against the Seljuqs without the distraction of the Latins for the time being. Nicaea was able to consolidate their eastern frontier for the remainder of the century. Hostilities broke out again in 1224, and a crushing Nicaean victory at the Second Battle of Poemanenum reduced Latin territories in Asia effectively only to the Nicomedian

Nicomedia

Nicomedia was an ancient city in what is now Turkey, founded in 712/11 BC as a Megarian colony and was originally known as Astacus . After being destroyed by Lysimachus, it was rebuilt by Nicomedes I of Bithynia in 264 BC under the name of Nicomedia, and has ever since been one of the most...

 peninsula. This treaty allowed the Nicaeans to go on the offensive in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 years later, culminating in the reconquest of Constantinople in 1261.