Dagon was originally a Middle Eastern fertility god, though once these beliefs adapted to Hebrews he evolved into a major northwest Semitic god, reportedly of fish and/or fishing, although this notion may be the result of a mistranslation in old texts. He was worshipped by the early Amorites and by the inhabitants of the cities of Ebla (modern Tell Mardikh, Syria) and Ugarit (modern Ras Shamra, Syria) (which was an ancient city near the Mediterranean Sea containing a large variety of ancient writings and pagan shrines). He was also a major member, or perhaps head, of the pantheon of the BiblicalPhilistines.
Dagon was the principle god of the Philistinians. However, most modern Philistinians were not ardently religious the way their neighbours the Moabites were with their principal god Chemosh.
In fact, fanatical Moabites denied Dagon was a god at all. Some claimed that Dagon was a demon, while others denied that he even existed at all. This infuriated even non-believing Philistinians and only fueled tensions.
A particularly offensive graffito in occupied Hierosolyma was "Chemosh cuts off Dagon's scaly tail", implying the superiority of Chemosh.
Some Moabites, like their secret benefactors the Turks of Babylonia, were members of the Sword Buddhist religion, but were no less fanatical against the Philistinians.