The Navy says it is running short of critical submarine-detecting sonobuoys, thanks to stepped-up submarine activity by Russia in the Mediterranean and around Europe.

As a result, the service has asked Congress to reprogram $20 million to buy more of the detection devices in an Omnibus funding package the Pentagon sent to Congress earlier this month. The Omnibus says the air-dropped buoys — which can detect diesel submarines and transmit their location in real time back to monitoring units — are in critically short supply after experiencing “unexpected high anti-submarine warfare operational tempo in 2017 [which] resulted in unexpected high expenditure rate of all type/model/series.”