The armed forces were on high alert to guard against any retaliation.

武装部队保持高度警惕，以防发生任何报复行为。

《柯林斯英汉双解大词典》

We were on high alert.

我们都处在高度戒备状态。

youdao

Without stress management, all too often your body is always on high alert.

不去控制压力，身体会一直处于高警戒状态。

youdao

Dr.Chan said all countries should immediately activate their pandemic preparedness plans and countries should remain on high alert for unusual outbreaks of influenza-like illness and severe pneumonia.

VOA: standard.2009.04.29

Speaking to local media, Pakistani Interior Minister Rehman Malik said intelligence agencies had expected attacks on security sites in the country and that authorities will remain on high-alert.

VOA: standard.2009.10.15

Security around the country is on high alert in the wake of Tuesday's terror assault.

CNN: Bomb threats close Boston Harbor

His book series 'The Rats' has kept me on high alert whenever I'm on the tube!!

CNN: UK bids farewell to chiller writer James Herbert

The home ministry has issued an advisory to all state governments to be on high alert.

BBC: India restaurant bomb blast kills nine in Pune