Step 1: Recall what preventive detention means.
Preventive detention allows the State to detain a person to prevent a future offence, rather than punishing a past one.
Step 2: Check when this power can be used.
Indian law allows preventive detention during ordinary peacetime as well as during war, and it does not depend on any emergency being proclaimed.
Step 3: Eliminate the other options.
Tying it only to internal emergency, national emergency, or wartime wrongly narrows a power that in fact applies at all times.
\[ \boxed{\text{At any time during peace or war, whether or not a proclamation of emergency has been made}} \]