->''[[http://www.youtube.com/watch?v=Y5Qo9iAB9q0 Dun-dun-dun-dun\\
Dun-dun\\
Dun-dun-dun-dun\\
Bwaaaaa~]]''
-->--''Anime/NeonGenesisEvangelion''

A war-deciding clash that may be a FinalBattle and takes place before TheEnd. A Decisive Battle is a chance for an organisation to [[StrategyVersusTactics turn the tide of a war in their favour]]. Whether it's of a greater scale than the clash(es) which end the war for good is neither here nor there. It can lead directly to the final conflict(s) or even set up the (premise of the) main story to be told.

Distinct from Space Battles in that not every battle in space is a Decisive one and not every Decisive Battle takes place in space. However, these scenes use many of the same methods - lots of extras, CGI, and miniatures for distant shots with close ups of the main actors, extras and stuntmen doing all the physical work. So this usually takes up a lot of the budget as the producers try to provide a thrilling and awesome setting for the audience to enjoy and tense up about. Historical battles can be an exception as many require little post-production work to look decent, though they can always use a bit of sprucing up. As they are drawn from RealLife they certainly can qualify for epic-ness depending on the battle and its circumstances.

The same clichés are also present as in the SpaceBattle as well, not all of them need to be used:
* The enemy will have a secret weapon which they plan to unleash to destroy all the heroes or to turn the tide of the battle
* It will be a pivotal point in the war and change the fortunes of one side and the fate of the world.
* The good guys will usually be vastly outnumbered, under equipped or at a disadvantage, however both sides can be equal as well.
* The battles make use of thousands of soldiers or vehicles taking part to show the scale of it (in most productions made after the late 1990s they will all be computer generated).
* Several or all of the main characters will be involved as well as several minor characters and background characters at once to show how everything is united in a common goal.
* The enemy will either be overconfident to the point they see no need in a backup plan or to send everything at the good guys, or they will charge everything in knowing they will win.
* When it looks like the enemy have all but won the battle, reinforcements show up save the day and win the conflict.
* The heroes will have a time limit in which they have to win, they will always achieve this with only a few seconds left.
* Someone will make a Heroic Sacrifice or perform a Heel Face Turn or Face Heel Turn.

These battles can overlap with the FinalBattle trope and the SpaceBattle trope. Although this depends on when they turn up in proceedings and what the genre is.

----
!!Examples:
* The Battle Of Chibi in both actual Chinese history and ''Literature/RomanceOfTheThreeKingdoms'': the combined yet still vastly outnumbered armies of Shu (led by Zhuge Liang) and Wu (led by Zhou Yu) against the ''massive'' naval fleet of Cao Cao's Wei. This battle is considered the one that finally establishes the three-way power struggle between the titular kingdoms, and is rightfully featured heavily in any adaptation of the novel.
** In ''VideoGame/DynastyWarriors 8'', the [[ForWantOfANail turning point]] that leads to Wei's [[WhatIf Hypothetical Route]] is Wei emerging victorious at Chibi.
* Two are featured in LordOfTheRings. The first is only alluded to in the books but shown in the films, that being the seige of Mordor where the Last Alliance of Elves and Men were able to defeat Sauron. However Isildur's refusal to destroy the ring ultimately led to the War of the Ring at the end of the third age.
** The other battle was the Seige of Minas Tirith in which Sauron attempted to topple Gondor and ensure his domain over Middle-Earth, however reinforcements from Rohan and then from Aragorn with several Dunedian and soldiers from south Gondor ensured that Mordor's army was routed, the king had returned, and what led to the FinalBattle outside the Black Gates which allowed Frodo to destroy the ring.
* Several in the ''CommandAndConquer'' series.
** In ''Red Alert'', the turning point of the war comes when the player manages to destroy the Iron Curtain. This leads to the Allies turning the war from defensive to counter-offensive.
** In ''Red Alert 2'', Tanya destroying Soviet nuclear weapons in Europe, allowing European nations to freely provide support to the US without fear of nuclear armageddon.
** ''Tiberian Sun'' has two: Unifying of Nod, which leads to Nod launching their major offensive and later the destruction of Nod's missile and Banshee facilities, leading to a GDI offensive that wins the war.
** The Battle of Temple Prime in ''Tiberium Wars'' was supposed to be the decisive strike that would break the resurgent Nod forces wide open, in a deliberate CallBack to ''Tiberian Dawn'', where the final GDI level also involved a strike at a Temple of Nod at Sarajevo. Although the attack is successful, it has [[AlienInvasion unforeseen consequences]]... (unforeseen [[JustAsPlanned except to Kane]], [[MagnificentBastard of course]]).
* Happens in ''VideoGame/{{Warcraft}}'' series.
** In ''Warcraft II: the Tides of Darkness'' the Horde was close to defeat the Alliance in the battle of Lordaerons capital city, but the Alliance won and started to turn the tide of the war because of the conflict between Doomhammer and Gul'dan. The Alliance were then able to drive the Horde all the way back to the Dark Portal. This is not how it is in the game itself (the Alliance campaign never has the Horde reach Lordaeron's capital, while the Horde campaign has the Horde ''win'' the battle even after Gul'dan's schemes ends with a several clans destroyed or too far to assist), but how things were described in later games and media (to explain how both campaigns were canonical, but the Alliance campaign was ''more'' canonical).
** The battle at Blackrock Spire after the failed siege is probably a better example. While the Alliance has indeed pushed the Horde back to the Spire, the Horde still had a chance to strike. Orgrim Doomhammer hoped that killing the supreme commander of Alliance forces, Lord Anduin Lothar would cause the Alliance forces to lose faith and be crushed. For a moment, it nearly happened. Then Lothar's NumberTwo Turalyon took command, captured Doomhammer, and routed the Horde.
* Several happen during the [[Series/StarTrekDeepSpaceNine Dominion War]]:
** Operation Return sees the Federation reclaiming Deep Space Nine and the annihilation of the Dominion's reinforcements from the Gamma Quadrant.
** The Second Battle of Chin'toka marks the Breen's first major engagement in the war, wiping out an entire fleet with unstoppable energy-dampening weapons.
* In UsefulNotes/WorldWarTwo there are several examples of battles which helped turn the tide in favour of the allies. The battle of Stalingrad was the big one [[note]] The Soviets let the Germans dangerously overextend and totally exhaust themselves trying to take the city while drip-feeding just enough men in to keep them from taking it... before launching a devastating surprise counter-offensive that encircled the entire German siege-force. Although ''Unternehmen Taifun'' had been a defeat, the Soviet counter-offensive that had followed it had not been well-planned enough to make it a ''decisive'' one[[/note]], with 200,000 German combat-troops (and 200,000 Rumanians+Italians) and all their heavy weapons being killed or forced to surrender - this being a full 1/8 of the Germans' entire combat-strength on the Ostfront (1.6 million), and 1/9 of their entire combat-strength. While this may not sound like much, take our word for it that Germany would take at least six months to replace those losses[[note]] Well. 'Six months' at all-out war-production levels, but in 1942 Hitler had refused to fully convert the German economy to a war-footing. It was only ''after'' Stalingrad that this was done. This is because replacing these losses with the 1942-level of production would take ''four years''. [[/note]]and there was no way in hell that the Soviets were going to give them that kind of time (after Stalingrad they went on to liberate the entire Caucusus and eastern Ukraine in four months, killing or taking prisoner another 100,000 German and 100,000 Rumanian+Italian combat troops). Before Stalingrad, some thought the Germans could win the war. After Stalingrad, even the Germans themselves knew that they would lose[[note]] If only because before Taifun/The Winter Counter-Offensive/Stalingrad, the Germans assumed that reality did not apply to them and they would beat absolutely anyone they made war upon. As early as 29/6/1941, the seventh day of the war with the USSR, Joseph Goebbels (German minister of propaganda) noted that "In foreign countries our military situation is, if anything, being judged rather too optimistically, even by our enemies. They think our Wehrmacht capable of the most amazing achievements." This can be seen even today, where it is hard to find any works from the USA which analyse the Wehrmacht for what it really was (deeply flawed institution that could only succeed against weaker opponents) and not the image it projected (flawless, invincible army of genius supermen that only failed because it was [[ZergRush drowned out by endless hordes of mindless inferiors/subhumans]]) [[/note]].
** Another turning point would be ''Unternehmen Zitadelle'', the German Summer Offensive of 1943. Not only did it fail, but it had no chance of succeeding because it was a great big trap just like Stalingrad. The Soviets let the Germans ''think'' they could pull it off so that they would try it. Again, like Stalingrad it wasn't the battle itself that destroyed the Germans - it was the eight months of non-stop campaigning throughout the summer, autumn, and winter that completely annihilated Germany's panzer forces and rendered her totally incapable of any kind of offensive action[[note]] Though, Hitler being Hitler, he forced Germany into ''three more'' small-scale offensives that she was frankly incapable of succesfully executing before the war's end - ''Wacht am Rhein'' (Ardennes, France, December-January 1945), ''Konrad'' (Budapest, January-February 1945) und ''Frühlingserwachen'' (Balaton, Hungary, March 1945)[[/note]]. Before ''Zitadelle'' people thought the war might last another five-six years. After ''Zitadelle'', people thought the war would be over within two-three years.
** The final turning point would be ''Operation Bagration'', the Soviet Summer Offensive of June-August 1944. In the first two weeks of it they killed 25k and captured 263k German combat troops (1/4 of Germany's ever-dimishing figure of 1,023,000 combat troops on the Ostfront and 1.2 million in total), and in the two months of it they liberated Belarus and reached the Vistula (killing or capturing at least another 50,000 German combat troops). Worse still, the reinforcement of the Allies' beach-head in France forced Germany to transfer as many as 100,000 combat-troops to the west to hold them back, leaving them with less than 600,000 combat-troops to face the Soviets' 2 million. Before ''Bagration'', people thought the war would be over in two-three years. After Bagration, people thought the war would end ''that year''[[note]] the people of Warsaw were so sure of this that they rebelled against German rule even as the Germans managed to counter-attack and push the Soviets' exhausted and overextended forces back from Warsaw. While it's true that the Red Army ''could've'' forced its troops to march on Warsaw, and taken extremely heavy losses in doing so, it's also true that Stalin did not want to do this for the sake of a political movement (Polish independence) he wanted destroyed anyway. The 'Warsaw Uprising' was brutally suppressed to the tune of more than 100,000 civilian dead. [[/note]] or in 1945 at the latest.
** El-Alamein was the turning point for the Commonwealth, putting the Germans on the defensive for virtually the rest of the war.
** The battle of Midway was the turning point for proceedings in the Pacific, where the American Navy was able to inflict a large enough blow on the Japanese that they were never able to recover for the rest of the way. It is widely considered the most important naval conflict in history.
** D-Day is perhaps the final and most iconic for the allies, 175,000 soldiers were able to establish a beachhead in Normandy and essentially destroy any remaining hope for an Axis victory.
** Most notably, the strategy adopted by the Imperial Japanese Navy during World War II turned around a [[http://en.wikipedia.org/wiki/Kantai_Kessen Decisive Battle]] where their fleet would crush the US one in a single, climactic battle. This strategy was epitomized on the massive ''Yamato''-class battleships. The US Navy, on the other hand, ultimately defied this trope between the loss of battleships at Pearl Harbor forcing the USN to rely on its carriers, the island-hopping strategy that intentionally avoided large concentrations of Japanese forces, and the massive industrial advantage the US had over Japan allowing it to replace its losses. It came to a head in the Philippines Campaign in 1944 (At The Battle of Leyte Gulf) when the last effective remnants of the worn-down IJN were torn to shreds.[[note]]While some would consider "The Marianas Turkey Shoot" to be this, at that battle the Japanese carriers and their escorts escaped despite the extreme damage to their aircraft squadrons. Leyte is when they were completely destroyed.[[/note]]
* The Spring Offensive in early 1918 during UsefulNotes/WorldWarOne. The United States had just entered the war on the side of Britain and France, and Germany knew it would lose the war if the massive industrial resources the Americans possessed were fully brought to bear. On the other hand, the Russians were no longer in the war thanks to the [[RedOctober Brest-Litovsk Treaty]] and so the Eastern Front was no longer a concern, freeing up nearly 50 divisions. Germany had a manpower advantage, but one that wouldn't last once the Americans came in. As a result, this large offensive was one last push to try to end the war on Germany's terms. From late March through mid April, the Germans gained the most ground since the start of the war before trench warfare settled in (Paris was within 50 miles of the front), but couldn't sustain the offensive nor hold it with their depleted reserves. With the Hundred Days' offensive that August, the German lines eventually collapsed and the German Empire capitulated in November.
* The penultimate battle in ''NexusTheJupiterIncident'' is the largest battle in the game. It involves your task force facing off against constant waves of whole enemy fleets periodically arriving via the wormhole to the Solar System. Not only is the battle incredibly tough, but you must constantly watch that your ships don't get too close to the wormhole lest they be sucked in. You ''may'' get some reinforcements, but that depends on your actions in previous missions (e.g. Chief Zatuk's ''Warcry'' will only arrive if you kept him alive during an impromptu EscortMission earlier). The final battle involves just your ship facing off against a massive Vardrag cityship while also fighting the massive gravitational pull of the Nexus.
* In ''Franchise/StarWars'', the separate destruction of both Death Stars are this. The first one at Yavin killed a number of the Emperor's best servants, especially Grand Moff Tarkin. However, it is subverted in that the Imperial Fleet was not damaged and a squadron of Star Destroyers was quickly sent to Yavin to quarantine the Rebels. A better example is the Second Death Star at Endor. Its destruction and the preceding space battle resulted in the death of the Emperor, Darth Vader, along with the loss of the flagship ''Executor'' and nearly half the fleet engaged. ExpandedUniverse material reveals that the ''Executor'' was the greater loss; while other leaders stepped in to fill the Emperor's shoes and frankly couldn't do worse than he had, the loss of the flagship (and the best and brightest of the officer corp that were serving on her) was a blow they didn't recover from until the war had turned against them.