Delaying Action

A delaying action is a battle fought by a clearly outnumbered and out-gunned force to try and hold up a superior force. The aim is to buy enough time for other friendly forces to a) escape or b) arrive.

This may involve a Heroic Sacrifice, but ideally, you aim to perform a Tactical Withdrawal before being slaughtered. The military equivalent of either You Shall Not Pass or holding a position until the Big Damn Heroes show up.

Examples of Delaying Action include:

Film

300, recounting the Spartans at Thermopylae (see Real Life below).
The Battle of Hoth in The Empire Strikes Back. The Rebels knew there was no way they could actually win: the Empire had better equipment (including heavy armor for which the Rebels had no viable counter) and too much of a numerical advantage. The ground forces and Rogue Squadron simply hoped to delay the Imps long enough to evacuate the base. The battle was considered an Imperial victory overall, though the Rebels technically achieved their objective.
Wing Commander has a single carrier being asked to hold off an entire Kilrathi fleet for 2 hours, while the main Confederate fleet gets into position.

Literature

In The Third World War, NATO successfully delays Soviet forces long enough for reinforcements to arrive, then launches a decisive strike and turns the Soviets back around Krefeld.
In Red Phoenix, North Korea invades South Korea. US and South Korean forces essentially have to fight one big delaying action until reinforcements can arrive from the US.
Rogue Squadron did this in Dark Force Rising, trying to buy time for Luke and Han to get into their ships and let Fey'lya escape with his force. Fortunately for them, Fey'lya was steered into an Engineered Public Confession and his people went back to help the Rogues. This wasn't enough. Karrde's smugglers showed up. This wasn't enough. Then Bel Iblis showed up. This was enough until a second Star Destroyer appeared, and it took two counts of Ramming Always Works before the day was saved.
- Wedge Antilles loves these, since his particular style of warfare makes them work. Case in point: the Siege of Borleais. All told, the siege involved an entire fake secret engineering project, an entire real secret engineering project, a planetary bombardment by the garrison defenders, a Super Star Destroyer dropping into the middle of the enemy fleet... oh, and the wholesale evacuation of the garrison before the final battle. Borleais cost two entire Vong fleets and a planetary garrison, and was a huge embarrassment to their command staff.
In The Silmarillion, the Men of the House of Hador delay the forces of Angband long enough for Turgon's Gondolindrim to escape unfollowed. All but one of them die, and it only gets worse for the survivor...

Live Action TV

In the final episode of Robin Hood The outlaws, who have seized Nottingham, try a gradual retreat to delay the Sheriff's forces until forces loyal to King Richard can arrive. It turns out they're not coming and a change of plan is needed.
An episode of Lie to Me features a CIA agent who'd went over to the Taliban redeeming himself by delaying them long enough for Lightman and the others to escape a bunker.
The Battle of the Line, in the Babylon 5 prequel movie In The Beginning:

President of Earth: "We have continued to broadcast our surrender and a plea for mercy. And they have not responded. We therefore can only conclude... that we stand at the twilight of the Human race. In order to buy more time for our evacuation transports to leave Earth, we ask for the support of every ship capable of fighting to take part in a last defense of our homeworld. We will not lie to you. We do not believe that survival is a possibility. We believe that anyone who joins this battle... will never come home. But for every ten minutes we can delay the military advance several hundred civilians may have a chance to escape to neutral territory. Though Earth may fall, the Human race must have a chance to continue elsewhere. No greater sacrifice has ever been asked of a people than I ask you now... to step forward one last time... one last battle, to hold the line against the night. May God go with you all."

Real Life

Hundreds of real-life examples, including:
- Part of the Battle of Gettysburg.
- Part of Dunkirk
- The battle of Thermopylae... which makes this one Older Than Feudalism.
  - Twice at least. A second battle during WWII took place but it was a withdrawal instead of a sacrifice.
  - According to one version Leonidas made sure that all of his three hundred were married men who Sparta could afford to lose as they had already reproduced and thus would not be hurting Sparta's population of warriors. This was against the normal custom of Kings having a guard of youths who needed promotions. Thus it appears that he had a pretty good idea that there was a strong chance he wouldn't be coming back.
This was a massive part of NATO plans for a World War Three in Europe. The aim was to trade ground for time to allow US forces to arrive. One must feel sorry for the West Germans in all this...
- Though with West Germany's insistence on "forward defense", that their country be defended right up to the border with East Germany it was really more like trading lives for NATO Army Groups to mobilize their corps and the mentioned REFORGER reinforcements to arrive.
A day or two before the battle of the Alamo, the commanding officer received a dispatch stating that reinforcements were on their way to him. Some historians now guess that the desperate defense of the fort there was not intended as a last stand, so much as a delaying action in hope that those reinforcements would arrive.
The Battle of the Phillipine Sea was a rough combination of this and Defensive Feint Trap. The American fleet was covering the Saipan invasion. Instead of launching a strike at first siting(doctrine for carrier warfare ever sense the Japanese lost Midway by not doing so), the Americans sheltered behind a gauntlet of fighters and shipborn anti-aircraft guided by new communication and sensory technologies that had not been available in the early days of carrier actions. The result was that Japan lost so many pilots it could not replace them and any carriers it lost were almost an afterthought.
- Similarly at Leyte Gulf the Japanese hoped to catch the American invasion force unloading with a prong through Suriago Straits and Samar Island. The first action involved the Japanese force being jabbed at all the way through by torpedo attacks until it reached the American line of battle waiting at the end which included battleships salvaged from Pearl Harbor and ended in a few conclusive salvos. Samar Island was the more dramatic action and also closer to this trope for the destroyers and escort carriers spent their time delaying the Japanese until their commander's nerve broke.

Video Games

The climactic Battle of South Moundtop in SaGa Frontier II is all about stalling for time. Unlike most of the other battlefield campaigns where there is either parity or conditions heavily in the players favor, this battle is against an army vastly your superior. Everything must go perfect for you to survive the necessary turns and your allies to arrive to finish the battle off screen.
Several times in Warcraft III. At least once you're stalling until the cavalry arrives. The climactic battle is you stalling until your trap is set.
The 3rd Terran mission in StarCraft involves this, where you must hold off the Zerg until rescue arrives.
- The Expanded Universe novel Speed of Darkness stars a group of Confederate Marines who fought a separate delaying action that apparently drew a sizable quantity of Zerg away from the Player Character.
  - It wasn't so much their resistance but the fact that they had a psychic beacon with them.
Happens by event during some battles in Hearts of Iron II and III. It slows the attacker down a bit and helps the defenders.
The level "Revenge of the Empire" in Rogue Squadron III: Rebel Strike. Mirroring the Hoth example, Rogue Squadron is providing air cover to the evacuation of the base on Yavin IV.