in the 5th century The earliest references to the Frisians are found in the works of Roman and Greek authors such as
Tacitus, as in his , and
Ptolemy, in his
Geography, calling these tribes the and the . Both Tacitus and Ptolemy describe the as living from north of the
estuary of the
Rhine to around the
Ems river. Although they were not a part of the
Roman Empire, the areas comprising
Frisia were akin to a
tributary state and some Frisians served as
mercenaries in the
Roman army. The appear to enter recorded history in
Drusus's account of the war against the Rhine Germans and the
Chauci in 12 BC. They occasionally appear in the accounts of Roman wars against the Germanic tribes of the region, up to and including the
Revolt of the Batavi around 70 AD. Frisian mercenaries were hired as cavalry to assist the
Roman invasion of Britain. They are not mentioned again until 296, when they were deported into Roman territory as
laeti (i.e., Roman-era
serfs; see
Binchester Roman Fort and
Cuneus Frisionum). The discovery of a type of earthenware unique to fourth century
Frisia, called
terp Tritzum, shows that an unknown number of them were resettled in
Flanders and
Kent, probably as
laeti under Roman coercion. It is unlikely that these Frisians described by the Romans were Germanic-speaking peoples.
Evidence from proper names suggests they spoke an
Indo-European language that was neither
Germanic nor
Celtic. How the original and were originally supplanted is somewhat unclear; Roman sources on the Frisians precede the earliest medieval ones by over three hundred years. From the third through the fifth centuries, Frisia suffered
marine transgressions that made most of the land uninhabitable, aggravated by a change to a cooler and wetter climate. Whatever population may have remained dropped dramatically, and the coastal lands remained largely unpopulated for the next two centuries. One theory is that the area became effectively abandoned by its original inhabitants and a Germanic group moved in, taking over the local name. The German linguist
Elmar Seebold suggests, for example, that the
Jutes integrated into the group relatively peacefully and the new Jutish–Frisian entity became a Jutish-speaking group, but ultimately assumed the Frisian name. Another theory suggests that the
Frankish elite named the region using the works of classical scholars and the name was eventually adopted locally; the Franks sometimes referred to areas on the periphery of
their empire by Roman-era names, including for modern-day
Utrecht and for the
pagus of Brabant. The Frisians then spread considerably over the following two hundred years, dominating the
North Sea region. This period is marked by the rule of
warlord-like kings and a
maritime economy augmented by considerable cattle-breeding skill. Frisian domination of North Sea trade during this era led some contemporary non-Frisian documents to refer to the North Sea as the Frisian Sea () and the term
Frisian was used in
Dorestad to mean any merchant, not necessarily an ethnic Frisian. This farthest extent of Frisian territory is sometimes referred to as ('Greater Frisia'). This period saw Frisia ruled by a
high king, with the earliest reference to such a leader being dated to 678AD. In the early eighth century, the Frisians mostly worshipped
Germanic gods such as
Thor and
Odin outside the vicinity of
Utrecht. Shortly thereafter, the Frisian nobles came into increasing conflict with the
Franks to their south, resulting in a
series of wars in which the
Frankish Empire eventually subjugated Frisia in 734. These wars benefited attempts by Anglo-Irish missionaries (which had begun with
Saint Boniface) to convert the Frisian populace to
Christianity, in which
Saint Willibrord largely succeeded. Some time after the death of
Charlemagne, the Frisian territories were in theory under the control of the
Count of Holland, but in practice the Hollandic counts, starting with
Count Arnulf in 993, were unable to assert themselves as the sovereign lords of Frisia. The resulting stalemate resulted in a period of time called the
Frisian freedom, a period in which
feudalism and
serfdom (as well as central or judicial
administration) did not exist; the Frisian lands only owed their allegiance to the
Holy Roman Emperor. During the 13th century, however, the counts of Holland became increasingly powerful and, starting in 1272, sought to reassert themselves as rightful lords of the Frisian lands in
a series of wars, which (with a series of lengthy interruptions) ended in 1422 with the Hollandic conquest of Western Frisia and with the establishment of a more powerful noble class in Central and Eastern Frisia. In 1524, Frisia became part of the
Seventeen Provinces and in 1568 joined the
Dutch revolt against
Philip II, king of Spain, heir of the Burgundian territories; Central Frisia has remained a part of the Netherlands ever since. The eastern periphery of
Frisia would become part of various German states (later Germany) and Denmark. An old tradition existed in the region of exploitation of peatlands. ==Migration to England and Scotland==