related discussion: keep one's powder dry - auf der Hut sein
Dictionary: auf der hut sein
to be on the watch = auf der Hut sein
to be wary of sth. = vor etw.dat. auf der Hut sein
to be alert (to sth.) = (vor etw.dat.) auf der Hut sein
to be on one's guard (against so./sth.) = (vor etw.dat.) auf der Hut sein
to look out for so./sth. = vor jmdm./etw. auf der Hut sein
to keep one's powder dry [coll.] = auf der Hut sein
off one's guard = nicht auf der Hut
https://www.ahdictionary.com/word/search.html...
keep (one's) powder dry = To be ready for a challenge with little warning.
https://www.oxfordlearnersdictionaries.com/de...
keep your powder dry
(old-fashioned) to remain ready for a possible emergency
https://www.collinsdictionary.com/dictionary/...
American: keep one's powder dry
Slang to be ready for action
https://www.merriam-webster.com/dictionary/ke...
keep one's powder dry
idiom old-fashioned
: to be calm and ready for a possible problem in the future
They don't know how the election will turn out, so for now they're just keeping their powder dry.
https://www.ldoceonline.com/dictionary/keep-y...
to wait calmly until you see how a situation develops before deciding what to do
https://www.nytimes.com/1997/02/23/magazine/k...
The purpose of keeping powder dry is to be able to blaze away at the proper time. Thus, the phrase keep your powder dry is not limited to ''stay calm'' but carries an implicit, most ominous threat: ''and be prepared to blow the enemy's head off at the propitious moment.''
https://www.phrases.org.uk/meanings/217500.html
What's the meaning of the phrase 'Keep your powder dry'?
Be prepared and save your resources until they are needed.
https://www.deutschlandfunkkultur.de/auf-der-...
Wer auf der Hut ist, der passt auf, der hält Wache und ist schlicht vorsichtig.
https://www.duden.de/rechtschreibung/Hut_Obhu...
Wendungen, Redensarten, Sprichwörter
[vor jemandem, etwas] auf der Hut sein ([vor jemandem, etwas] vorsichtig sein, sich in Acht nehmen; Soldatensprache, eigentlich = auf Wache im Felde außerhalb des Heerlagers stehen)
I agree with jwtkac and w that "keep one's powder dry" has an element of being prepared to act when necessary. The German phrase "auf der Hut sein" seems to me to be more to be wary or on guard. Perhaps my understanding of the German phrase is not broad enough, however.
Could this be revisited? I would be interested in more opinions.
