The Cuban government has announced it will hold five days of nationwide military exercises to prepare for "a range of enemy action".
Cuba did not link the exercises to the victory of Republican candidate Donald Trump in the US presidential election.
But analysts say such exercises have in the past been held at times of tension or to send a signal to the US.
During his campaign, Mr Trump said he would reverse the recent thaw in relations between Cuba and the US.
Cuba's Ministry of Defence announced the move in the government-run newspaper Granma.
It said the manoeuvres, dubbed Bastion Strategic Exercises, would be held from 16 to 18 November, with two extra days of exercises marking Cuba's National Defence Days on 19 and 20 November.
It said they would serve to "prepare the troops and the population to counter a range of enemy action".
Read about the sticking points holding back US-Cuban ties
They will include the movement of troops and "war material as well as fly-overs and explosions where required", the statement read.
The first time Bastion Strategic Exercises were held was in 1980, shortly after the election of Ronald Reagan as US president.
Mr Trump's election comes less than two years after current US President Barack Obama and Mr Castro announced a thaw in the fraught relations between the two countries.
Since then, there have been a series of symbolic and practical moves further narrowing their ties, including:
- Cuba opening an embassy in Washington, DC
- Washington re-opening its embassy in Havana
- President Obama visiting Cuba
- Easing of travel restrictions including the resumption of direct flights
- Relaxing of trade restrictions but no lifting of the long-standing US trade embargo
- Mr Trump has not been entirely clear about what his Cuba policy would be.
While he has said that he agrees in principle with "the concept of opening with Cuba" he said that the US "should have made a better deal".
In a tweet, he also accused President Castro of lacking respect for not greeting President Obama at the airport.
During a debate on CNN he said that he would close the US embassy in Havana "until such time as a really good deal could be struck".
Mr Trump has also expressed his backing for the US trade embargo in the past.