Tom Selleck portrays General Dwight D. Eisenhower - US Army – also known by his nickname of "Ike", hence the title. The film emphasizes the difficult decisions he had to make while dealing with the varied personalities of his direct subordinates, including General Omar N. Bradley - US Army (James Remar), Lieutenant General George S. Patton, Jr. - US Army (Gerald McRaney), General Bernard Montgomery - British Army (Bruce Phillips) and GeneralCharles De Gaulle - Free French (George Shevtsov).

The film does not have action sequences, focusing instead on the inner dealings of Supreme Headquarters Allied Expeditionary Force that led to the successful D-Day invasion of World War II. The film concentrates on decisions actually made by Eisenhower and the pressure brought to bear on him personally, including his personal relationship with British Prime Minister Winston Churchill (Ian Mune). His Chief of Staff, Lieutenant General Walter Bedell Smith - US Army, is also portrayed in the film, by Timothy Bottoms.

The film is also notable for being the only major video or film production in which General Montgomery's portrayal concentrates on his role as a competent military professional instead of focusing on his alleged personality disorders while still showing his egocentrism and foibles. General Patton's complex personality is also shown in a very brief set of scenes played by Gerald McRaney.

The film also mostly omits Ike's relationship with Kay Summersby though it is believed she appears briefly in the scene where the general officers are viewing the movie reels.

Countdown to D-Day was filmed entirely in New Zealand with the British parts played by New Zealanders. The American parts were played by Americans. 

U.S. Army Air Corp Major General Carl Spaatz, is incorrectly referenced as "Jimmy" Spaatz.

The movie accurately depicts the incident which nearly torpedoed Overlord. In a drunken scene at a restaurant, Major General Henry Miller — a West Pointclassmate of Eisenhower — of the USAAF blurted out the general time and place of Overlord. A lieutenant of the 101st Airborne overheard this and reported it up the chain of command. Miller was sent home with a reduced rank of Lieutenant Colonel.

Maj. Gen. Bedell-Smith spoke to the lieutenant and reported that the officer felt bad about doing what he did, but that he was worried about the lives of his men on the day they went to war without letting the Germans know when and where. Eisenhower on hearing this said the officer was better than Miller. He told Miller that it was their longstanding friendship that prevented him from seriously court-martialing him.

The film also makes reference to a message composed by Eisenhower to be given to the press corps in the event the invasion failed. This message was found, years later, in a pocket of General Eisenhower's old uniform. In this speech, Eisenhower accepted full responsibility for any failure of the assault.

In the US Armed Forces at the time, flag ranks were not always permanent and many were temporarily granted to senior officers through the use of Army of the United States ranks (before the 20th century, it was called brevetting). Often if an officer was relieved due to other honorable conditions, he would be returned to his original rank in the Regular Army. As Bedell-Smith put it: "You'd lose your theater rank. They'll take three of those stars." In the Miller case he was going to be returned home a major. Instead Ike asked that he be kept a Lt. Colonel instead.

The scene at the end of the film showing the visit to the 101st airborne troops is presented to the viewer as being on June 6, 1944. This particular gathering took place on the eve of D-Day on June 5, 1944, prior to the take-off to France.