Havana , Cuba ( CNN ) -- Cuba is wrapping up its biggest military exercises in five years , saying it wants to be prepared in the event of a U.S. invasion . Under the watchful eye of Cuban President Raul Castro , the armed forces is ending four days of extensive maneuvers , war-room strategy sessions and military parades across the island . `` This is a necessity of the first order , '' Gen. Leonardo Andollo Valdez said on state television . `` The political , military situation , which characterizes the confrontation between our country and the empire , can go from a relatively normal situation to a much more urgent , confrontational , aggressive one in a month , a week , or even in a night , '' he added . Cuban television broadcast images of camouflaged troops firing from trenches and fighter aircraft dropping bombs . Many of the images are from exercises in previous years . The exercises come amid a slight thaw in relations between the Cold War enemies . President Obama has lifted restrictions on Cuban-American travel and remittances , and the two countries have resumed immigration talks . Obama recently said the United States has no intention of invading the communist island just 90 miles off its coast . But the fear of an attack has been a constant concern here , and not without reason . In 1961 , Washington backed an invasion by Cuban exiles bent on overthrowing Fidel Castro , the brother of Raul Castro and former president of Cuba . They were defeated at the Bay of Pigs , but the United States has maintained an economic embargo , and Fidel Castro has survived numerous attempts on his life . The massive military exercises began in 1980 and have been repeated every few years . The latest maneuvers , called `` Bastion 2009 , '' are the first since Raul Castro succeeded his brother and Obama assumed the White House . Preparations for the exercises began in 2004 , before either was in office . The exercises end Saturday , and on Sunday , Cuba will celebrate Day of Defense .
Nation wrapping up its biggest military exercises in five years . Four days of maneuvers , war strategy sessions , military parades set across island . Cuban TV shows troops firing , aircraft dropping bombs ; many images are from previous years . Comment: