The phrase "army at work" is correct and usable in written English.
It can be used to describe a group of people working diligently or collaboratively towards a common goal, often in a structured or organized manner.
Example: "The volunteers formed an army at work, tirelessly preparing meals for those in need."
Alternatives: "team in action" or "group in operation".
Hacking isn't only done by governments and individuals; there are zombie hacker armies at work everywhere (Brian spent part of last week fighting off Russian hackers).
E1 Business INSURERS AT WORK -- An army of claims adjustors are working to revive companies that were damaged, destroyed or forced to close.
There's no doubt that an unseen army was at work behind the scenes, on every aspect of the production, and I owe them gratitude.
Some people say his private army is already at work, although it is not certain who is responsible.
Four thousand men, drawn from the security forces -- the National Guard and the Treasury Police -- and from regular units of the Salvadoran Army, were hard at work.
Arrest warrants for 50 more officers were issued this month, after the shooting down of a Turkish fighter jet by Syria, on the ground that the honey trap was aimed at army personnel working at radar installations.
Yet as people stake spheres of safety for themselves and their loved ones, their chosen courses of action expose an army of private demons at work.
Within hours of pulling out of Jabaliya, the army's bulldozers were at work again in another Gaza refugee camp, Rafah.
At St. Lythan's burial chamber against a backdrop of rolling fields and winter sunshine there was a small army of volunteers hard at work with spades in hand.
During the war Ms. Bell was a research assistant at the Ministry of Information, and just after the war ended in 1945 she was recruited to join the Monuments Men — the Monuments, Fine Arts and Archives Section — which had been created in 1943 by the Allied armies and was still at work, although hostilities had ceased.
