Trpimir II was a King of Croatia

Kingdom of Croatia (medieval)

The Kingdom of Croatia , also known as the Kingdom of the Croats , was a medieval kingdom covering most of what is today Croatia and Bosnia and Herzegovina in the Balkans.Established in 925, it ruled as a sovereign state for almost two centuries...

 from 928 to 935. He was from the House of Trpimirović. Trpimir was probably the son of Duke Muncimir

Muncimir of Croatia

Muncimir was a knez of Dalmatian Croatia who reigned from 892 to 910. He was a member of the House of Trpimirović....

 and younger brother of Tomislav.

Following the death of Simeon I of Bulgaria

Simeon I of Bulgaria

Simeon I the Great ruled over Bulgaria from 893 to 927, during the First Bulgarian Empire. Simeon's successful campaigns against the Byzantines, Magyars and Serbs led Bulgaria to its greatest territorial expansion ever, making it the most powerful state in contemporary Eastern Europe...

, Byzantium

Byzantium

Byzantium was an ancient Greek city, founded by Greek colonists from Megara in 667 BC and named after their king Byzas . The name Byzantium is a Latinization of the original name Byzantion...

 no longer needed Croatia's military support and repealed its alliance. Previously, Byzantium relied heavily on the Croats to threaten Symeon from the west. Despite the achievements of King Tomislav

Tomislav

King Tomislav was a ruler of Croatia in the Middle Ages. He reigned from 910 until 928, first as Duke of Dalmatian Croatia in 910–925, and then became first King of the Croatian Kingdom in 925–928....

 in halting Bulgaria's expansion, Byzantium reversed Croatia's supremacy over the Dalmatia

Dalmatia

Dalmatia is a historical region on the eastern coast of the Adriatic Sea. It stretches from the island of Rab in the northwest to the Bay of Kotor in the southeast. The hinterland, the Dalmatian Zagora, ranges from fifty kilometers in width in the north to just a few kilometers in the south....

n thema, which fell once again under its administration. However, Byzantine administration was nominal.

Trpimir's woes did not stop there. Pope Leo VI abolished the Nin

Nin, Croatia

Nin is a town in the Zadar county of Croatia, population 1,256 , total municipality population 4,603 .Nin was historically important as a centre of a Christian Bishopric in the Middle Ages. Up to the abolition and Latinization imposed by King Tomislav in the first half of the 10th century, Nin was...

 Bishopric in 928 and transferred Bishop Grgur

Gregory of Nin

Gregory of Nin was a medieval Croatian bishop who strongly opposed the Pope and official circles of the Church and introduced the Croatian language in the religious services after the Great Assembly in 926. Until that time, services were held only in Latin, not being understandable to the majority...

 to Skradin

Skradin

Skradin is a small town in the Šibenik-Knin county of Croatia it has a population about 3,986 . It is located near the Krka river and at the entrance to the Krka National Park, from Šibenik and from Split...

, in what was seen as a humiliating defeat for pro-Slavic proponents in the long running dispute between the Split

Split (city)

Split is a Mediterranean city on the eastern shores of the Adriatic Sea, centered around the ancient Roman Palace of the Emperor Diocletian and its wide port bay. With a population of 178,192 citizens, and a metropolitan area numbering up to 467,899, Split is by far the largest Dalmatian city and...

 and Nin Bishoprics.

The De Administrando Imperio

De Administrando Imperio

De Administrando Imperio is the Latin title of a Greek work written by the 10th-century Eastern Roman Emperor Constantine VII. The Greek title of the work is...

mentions that in the time of Trpimir, Croatia had a significant merchant fleet that traded across the entire Adriatic Sea

Adriatic Sea

The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...

.