Military bosses have spent £23m on supplies to prepare for when the UK is set to leave the EU on March 29.
The preparations are called Operation Yellowhammer and are part of the government’s emergency planning.
It comes after fears have grown over the difficulties of importing and exporting daily goods after Brexit.
Ammunition, spare parts, fuel and food are being gathered at military bases in Gibraltar, Cyprus and the Falklands.
“An army marches on its stomach. If supply lines breakdown they struggle,” a source told Sky News.
Gibraltar routinely sees UK military operations on its territory and thousands of soldiers and sailors could be affected by a lack of supplies.
A Ministry of Defence spokesperson told Sky News that the UK is working to ‘ensure that essential defence tasks would not be affected by a no-deal Brexit’.
They added: “The Ministry of Defence routinely undertakes contingency planning, and it is absolutely right that the government ensures we are prepared and resourced for a range of scenarios when we leave the EU.”