Lower Rhine in the context of Operation Market Garden

Cologne (/kə.ˈloʊn/ kə-LOHN; German: Köln [kœln] ; Kölsch: Kölle [ˈkœ̂lə] ) is the fourth-most populous city of Germany and the largest city of the German state of North Rhine-Westphalia with nearly 1.1 million inhabitants in the city proper and over 3.1 million people in the Cologne Bonn urban region. Cologne is also part of the Rhine-Ruhr metropolitan region, the second biggest metropolitan region by GDP in the European Union. Centered on the left bank of the Rhine, Cologne is located on the River Rhine (Lower Rhine), about 35 kilometres (22 mi) southeast of the North Rhine-Westphalia state capital Düsseldorf and 22 kilometres (14 mi) northwest of Bonn, the former capital of West Germany.

The city's medieval Cologne Cathedral (Kölner Dom) was the world's tallest building from 1880 to 1890 and is today the third-tallest church and tallest cathedral in the world. It was constructed to house the Shrine of the Three Kings and is a globally recognized landmark and one of the most visited sights and pilgrimage destinations in Europe. The cityscape is further shaped by the Twelve Romanesque churches of Cologne. Cologne is famous for Eau de Cologne, which has been produced in the city since 1709; "cologne" has since come to be a generic term.

The Heruli (also Eluri, Eruli, Herules, Herulians) were one of the smaller Germanic peoples of Late Antiquity, known from records in the third to sixth centuries AD. The best recorded group of Heruli established a kingdom north of the Middle Danube, probably including the area north of present day Vienna. This kingdom was a neighbour to several other small and short-lived kingdoms in the late 5th century and early 6th century, including those of the Sciri, Rugii, Danubian Suebi, and Gepids. After the conquest of this Heruli kingdom by the Lombards in 508, splinter groups moved to Sweden, Ostrogothic Italy, and present-day Serbia, which was under Eastern Roman control.

The Danubian Heruli are generally equated to the "Elouri" who lived near the Sea of Azov during the late 3rd or early 4th century, and are believed to have migrated westwards. In 267-270 these Elouri took part together with Goths and other eastern European peoples in two massive raids into Roman provinces in the Balkans and Aegean Sea, attacking not only by land, but notably also by sea. The equation of these "ELuRi" with the "ERuLi" was made by several Byzantine authors, and is still widely accepted although some scholars such as Ellegård consider this equation uncertain, and propose that the Heruli homeland lay elsewhere. For example, because a group of 6th century Heruli moved from the Danube to Scandinavia, some scholars believe that the Heruli had their earliest origins in Scandinavia. There are also proposals that there were Heruli kingdoms in several parts of Europe, already in the 3rd and 4th century, perhaps with common origins in the north. One proposal, based upon indirect evidence, is that there was a "Western Heruli" settlement based near the Lower Rhine, because in 286 AD, only a few years after the eastern raids, the Heruli were defeated in an attack on Roman Gaul.

Upper Rhine (German: Oberrhein [ˈoːbɐˌʁaɪn] ; French: Rhin Supérieur is the section of the Rhine between the Middle Bridge in Basel, Switzerland, and the Rhine knee in Bingen, Germany. Representing kilometres 167 to 529 of the river it is surrounded by the Upper Rhine Plain (Oberrheinische Tiefebene). Most of its upper section marks the France–Germany border.

The Upper Rhine is one of four sections of the river between Lake Constance and the North Sea, and is succeeded downstream by the Middle Rhine and Lower Rhine; only the High Rhine and Alpine Rhine lie above it. The countries and states along the Upper Rhine are Switzerland, France (Alsace) and the German states of Baden-Württemberg, Rhineland-Palatinate and Hesse. The largest cities along the river are Basel, Mulhouse, Strasbourg, Karlsruhe, Mannheim, Ludwigshafen and Mainz.

In historical and comparative linguistics, Low Franconian is a linguistic category used to classify a number of historical and contemporary West Germanic varieties closely related to, and including, the Dutch language. Most dialects and languages included within this category are spoken in the Netherlands, northern Belgium (Flanders), in the Nord department of France, in western Germany (Lower Rhine), as well as in Suriname, South Africa and Namibia.

High Rhine (German: Hochrhein, pronounced [ˈhoːxˌʁaɪn] ; kilometres 0 to 167 of the Rhine) is the section of the Rhine between Lake Constance (Bodensee) and the city of Basel, flowing in a general east-to-west direction and forming mostly the Germany–Switzerland border. It is the first of four named sections of the Rhine (High Rhine, Upper Rhine, Middle Rhine, Lower Rhine) between Lake Constance and the river delta at the North Sea.

Middle Rhine (German: Mittelrhein, pronounced [ˈmɪtl̩ˌʁaɪn] ; kilometres 529 to 660 of the Rhine) is the section of the Rhine between Bingen and Bonn in Germany. It flows through the Rhine Gorge (Oberes Mittelrheintal), a formation created by erosion, which happened at about the same rate as an uplift in the region, leaving the river at about its original level, and the surrounding lands raised. This gorge is quite deep, about 130 metres (430 ft) from the top of the rocks down to the average water-line.

The Middle Rhine is one of four sections of the Rhine between Lake Constance and the North Sea (the others being the High Rhine, Upper Rhine and Lower Rhine). The upper half of the Middle Rhine (Rhine Gorge) from Bingen (Rhine-kilometer 526) to Koblenz (Rhine-kilometer 593) is a UNESCO World Heritage Site, a striking cultural landscape with more than 40 castles and fortresses from the Middle Ages, unique terraced vineyards, and many wine villages. The lower half, from Koblenz (Rhine-kilometer 593) to Bonn (Rhine-kilometer 655), is famous for the formerly volcanic Siebengebirge, with the Drachenfels volcano. Both parts together are known as "the romantic Rhine".

In linguistics, Old Dutch (Modern Dutch: Oudnederlands) or Old Low Franconian (Modern Dutch: Oudnederfrankisch) is the set of dialects that evolved from Frankish spoken in the Low Countries during the Early Middle Ages, from around the 6th to the 12th century. Old Dutch is mostly recorded on fragmentary relics, and words have been reconstructed from Middle Dutch and Old Dutch loanwords in French.

Old Dutch is regarded as the primary stage in the development of a separate Dutch language. It was spoken by the descendants of the Salian Franks who occupied what is now the southern Netherlands, northern Belgium, part of northern France, and parts of the Lower Rhine regions of Germany. It evolved into Middle Dutch around the 12th century. The inhabitants of northern Dutch provinces, including Groningen, Friesland, and the coast of North Holland, spoke Old Frisian, and some in the east (Achterhoek, Overijssel, and Drenthe) instead spoke Old Saxon.