Yes, that's why I carefully worded it "... most of Northern and Western Europe and it's colonies."
In the mind of most Celtic scholars, contemporary Germany is not a Celtic country, although the lines between Slavic and Celtic don't seem as clearly drawn to me there as elsewhere. The name "Germany" came from the Celtic Germani tribe, which moved on north and westward long ago...
That said, in a broader sense much of the history of Europe over the millennia has been of wars between Celtic tribes.