A Green Goddess fire crew came to the aid of a woman who accidentally locked her baby inside her car.
The military personnel broke the car window before handing the child, unharmed, to the anxious mother.
The incident in Kingsley Road, Brighton, shortly after 5.25pm yesterday was one of just a handful of incidents attended by Green Goddess crews on the first day of the latest 48-hour strike by firefighters.
A spokesman for Military Media Operations, which is handling 999 fire calls from Sussex Police headquarters, said yesterday had been "very quiet".
He said: "We only had seven calls during the day and none of them were to fires."
Firefighters broke their picket for the first time during their strike to attend a head-on collision on a busy road.
Crews were sent to a smash between a Honda Accord and a Ford Maverick at Cross Levels Way, Eastbourne, yesterday.
However, they returned to their picket line at their Whitley Road station when they found out no lives were at risk.
One Eastbourne-based Green Goddess and two breathing apparatus rescue teams attended just before 3.30pm. No one suffered life-threatening injury. The road was closed for more than 30 minutes as police inquiries continued into how the crash happened.
Eastbourne station manager Paul Sundaram-Hardwick said: "As soon as we realised life was not at risk we went back. However, we are all desperately hoping that there is a resolution to the strike action."
On the evening picket line outside Brighton fire station, morale among the strikers remained high.
Firefighter Steve Petch, a senior member of White Watch, said: "The support from the public through tooting horns and money to the hardship fund has been better today than for our one-day strike last week."
The current strike will continue until 9am tomorrow and will be followed by a further 48-hour walkout from 9am on Saturday.
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