"High Germany" certainly seems to have been used in Britain quite late, if the book in #1 is anything to go by. Some more references:
In our first selection, High Germany, young Willy appears to believe that war will be a jolly lark, a sort of tourism with a musket; he attempts to persuade his true Love to accompany him. Sensible Polly points out that the theater of war is no place for a tender-footed, pregnant lass. The reference to British troops campaigning in "High Germany," as opposed to their more familiar ground in the Low Countries, almost certainly dates these lyrics from the time of the War of the Spanish Succession (1701-1714), particularly the Duke of Marlborough's Blenheim Campaign of 1704.http://www.wargame.ch/wc/nwc/newsletter/23rd_...
"'High Germany' is an old British folk song, which refers to the Duke of Marlborough's campaigns in Bavaria, or High Germany, where he fought the battle of Blenheim/Blintheim. Although I can't confirm the following details, I believe that the song is from the period it alludes to, has more than one tune, and that there are several variations on the words, as well as later adaptations to other wars." http://www.everything2.com/index.pl?node_id=1...
Traditional Ballad Index:
DESCRIPTION: Young man, conscripted into the war in Germany, bids his sweetheart come with him. She demurs, saying she is not fit for war. He offers to buy her a horse, and also to marry her by and by. She laments the war (and/or her pregnancy)
KEYWORDS: love war soldier
1714 - Hannoverian succession causes Britain to become involved in German wars
FOUND IN: Britain(England)
REFERENCES (4 citations):
Sharp-100E 56, "High Germany" (1 text, 1 tune)
Silber-FSWB, p. 279, "High Germany" (1 text)
BBI, ZN3231, "O cursed be the wars that ever they began" (?)
DT, WARGRMNY* WARGRMN2*
cf. "Jack Monroe" [Laws N7]
cf. "William and Nancy I" [Laws N8]
cf. "The Banks of the Nile (Men's Clothing I'll Put On II)" [Laws N9]
cf. "The Manchester Angel"
cf. "Across the Blue Mountain" (floating lyrics)
The Wars of Germany
Notes: Sharp cites a date of c. 1780 for this song. That the current forms of the song date from the eighteenth century is almost a historical necessity. The Hannoverian Succession (1714) brought a German prince to the British throne, meaning that English troops might be sent to intervene in German affairs. British interest in Germany ended when Napoleon rebuilt the Holy Roman Empire on his own terms, leaving the Hannoverian princes out of the picture. - RBW
(long discussion here)