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》

The cave fish, on the other hand, remain on high alert, patrolling their habitats even after hours.

而另一方面，穴居鱼仍然保持高度警惕，三更半夜还在居住的地方游来游去。

youdao

Both sides put their nuclear forces in high alert.

双方的核力量都在高度戒备中。

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

Also, why was it necessary for Stevens to be in Benghazi with its out-of-control security situation on what should have been a high-security-alert day of Sept. 11?

CENTERFORSECURITYPOLICY: A call to courage over Benghazi

The nation's civilian "high" alert -- the second highest level of warning -- was put in place Tuesday.

CNN: Al-Jazeera airs purported al Qaeda message

Bangladesh has put troops on high alert along the 200-kilometer border with Myanmar, said Shamsul Haque, Bangladesh's state minister for home affairs.

CNN: STORY HIGHLIGHTS