Some of the greatest warships have gone on to shape the history of the world and have even pushed their crews into unbelievable and incredible acts of bravery. Take a look at the very first submarine which is rumored to have lurked beneath New York harbor during the Revolutionary War, the smaller ships that rescued thousands from Dunkirk, or the destroyer in the Cuban Missile Crisis. Over the years, conflicts and wars have prompted extreme advances to ship designs and now they are faster, stronger, and smarter than ever before.

"I have no problem sacrificing myself for someone else. It's my job." So says a member of the elite Combat Rescue unit of the U.S. Air Force, whose job it is to come to the aid of American or Allied forces who are either injured or are in extreme danger. "Inside Combat Rescue," the result of unprecedented access provided to National Geographic Channel, takes viewers inside the harrowing world of the brave airmen -- Pararescuemen or PJs, as they're known -- during a four-month deployment to Kandahar, Afghanistan. More than two dozen missions are chronicled in the series, using strategically placed cameras on airmen's helmets and more than 40 cameras mounted both inside and outside of the Air Force's Pave Hawk helicopters. PJs and their rescue teammates race against time to save Americans, coalition forces, Afghan allies and even local Afghan families caught in the crossfire within the "golden hour," the critical first hour that's often the difference between life and death.

Missions involving the U.S. Air Force personnel stationed at Bagram Airfield in Afghanistan.

The trajectory of the war in Afghanistan, from toppling the Taliban to the present day.

In "The Hunt for Eagle 56," Smithsonian Channel follows the Nomad Exploration Team as it makes the stunning discovery of the USS Eagle 56 shipwreck off the coast of Maine. The team is made up of citizen-historians and amateur divers who set out to solve a 74-year-old naval mystery. The three-part series features interviews with relatives of Eagle 56 sailors and accounts from survivors. It also provides never-before-seen images of the lost warship lying at the bottom of the Atlantic Ocean. Missing for more than 74 years, the sinking of the World War II warship was long believed to be the result of a boiler room explosion. Now, the team pieces together the evidence to prove that a German U-boat torpedoed the ship in April 1945 just five miles off shore, killing 49 of the 62 crew members on board. The team presents its finding to the U.S. Navy, which, in turn, changes its classification from accidental to combat loss due to enemy action.

Stories of some of the greatest and deadliest submarine patrols of World War II.

A century after the war was fought, this five-part series explores whether or not World War I could have been avoided and how people endured the battles for four years. The program uses more than 500 hours of colorized, archival footage -- much of which has not been seen previously -- to tell the story of the worldwide conflict on a human level. Viewers are transported into the heart of battle -- in countries that include France, Russia and Palestine -- and inside the day-to-day lives of civilians behind the front lines.