context: From their original homelands in Scandinavia and northern Europe, Germanic tribes expanded throughout northern and western Europe in the middle period of classical antiquity; southern Europe in late antiquity, conquering Celtic and other peoples; and by 800 CE, forming the Holy Roman Empire, the first German Empire. However, there was no real systemic continuity from the Western Roman Empire to its German successor which was famously described as "not holy, not Roman, and not an empire", as a great number of small states and principalities existed in the loosely autonomous confederation. Although by 1000 CE, the Germanic conquest of central, western, and southern Europe (west of and including Italy) was complete, excluding only Muslim Iberia. There was, however, little cultural integration or national identity, and "Germany" remained largely a conceptual term referring to an amorphous area of central Europe.
question: By when did the Germanic tribes conquer the Celtic peoples?
answers.text: in late antiquity late antiquity late antiquity by 800 CE 800 CE