In movies, we see heroes getting rescued at the last minute all the time. This is done for dramatic effect - in reality, such last minute, convenient rescues are rare. But are there notable historical moments where, for one reason or another, a person or group of people actually were conveniently rescued at the last possible moment?
The Rampjaar, the annus horribilis of the Dutch Republic in 1672
It wasn't a matter of minutes, but in 1672 the predicament of the Dutch Republic went from utterly hopeless to a fighting chance in a matter of days:
Prelude and initial phase of the war
In 1670, Charles II of England and Louis XIV of France signed the Secret Treaty of Dover, in effect creating a secret pact between England and France against the Dutch Republic; even though at this point, the English were still part of the Triple Alliance against France. Louis XIV's ambition, ever since the War of Devolution (against Spain), was to make the Rhine the 'natural border' of France, which required the elimination of the Dutch Republic. Charles II, on the other hand, was a Catholic monarch in a Protestant-dominated state, who, in the long run, sought to restore Catholicism in England with French monetary and military assistance.
Charles II and Louis XIV both knew that such an alliance (England allying with a Catholic state against a fellow Protestant one) would not be popular in England and hence were poised to provoke a war with the Dutch as soon as possible. In August of 1671 the English used Machiavellian tactics in order to instigate conflict: according to the English Acts of Trade and Navigation, the Dutch were required to salute British warships by striking their flag and firing a salute. When the Dutch failed to do so with HMS Merlin, an 8 (!) gun sloop (only striking their flag but failing to fire a canon in salute) the English eagerly took this as a personal insult. When the formal complaint and demand for an apology by the English ambassador was dismissed by the Dutch Estates-General, the English had their pretext for war.
On April 6th 1672, England declared war on the Dutch Republic, beginning the Third Anglo-Dutch War. The next day, the French honoured their secret alliance and declared war as well, marching north a massive army under Louis, Grand Condé (the winner of the Battle of Rocroi) whilst Louis XIV's German allies (the Electorate of Cologne and Prince-Bishopric of Münster, both immediately adjacent to the Dutch Republic) invaded from the east.
The Dutch Republic was effectively cornered. Enemy armies were rapidly encroaching to its South and East and an hostile fleet was sailing towards its North and West. To make matters even worse, the country was on the brink of civil war and (at this point) had no allies to come to its aid. The mood in the Republic is epitomized by the famous Dutch adage het volk was redeloos, de regering radeloos en het land reddeloos (the people were despairing, the government overwrought and the country beyond saving) which is a very poetic way of capturing the sheer panic that swept the country.
The French advance was so rapid and successful, that on 19 June 1672 the French army stood less than 25 km outside of the capital of Amsterdam and had reduced the Dutch field army to a mere 8000 soldiers. Over 30 fortified towns had been taken. The French had brought the Dutch to their knees and forced them to enter negotiations for a formal surrender. It appeared the French had in two months succeeded in doing, where the Spanish had failed for 80 years.
Deus ex Machina moment
However ... at the same time there occurred a rapid succession of unlikely events that changed the course of the war and indeed much of the following century.
On the 7th of June, the outnumbered Dutch fleet under De Ruyter had engaged and unexpectedly defeated the English at the Battle of Solebay, ending the prospect of an English blockade of the Dutch coast.
At the very same moment the Dutch, in their desperation, resorted to their last defensive measure: the Dutch water line. This was not an ordinary ring of fortifications, but one of inundations. The Dutch opened the sluices and (during the initial peace negotiations) let the sea in, effectively transforming the most populated and core area of the Dutch Republic ... into an island. The French army now had no way of entering the heart of the Dutch Republic.
Louis XVI was not particularly worried though and expected the erupting Dutch civil war to end the war for him. He expected the ruling Republican faction to be defeated by the Orangist faction (those in favor of a mixed monarchical-republican state) who would then be more than likely to accept his demands in order to consolidate their position. However Louis XIV's demands were so incredibly harsh, demanding the outright annexation of 2/3 of the Dutch Republic and a huge indemnity, that he unintentionally turned the nation-wide mood of defeatism into one of determined resistance.
In a period of less than a week, the Dutch situation went from utterly hopeless and on the brink of total collapse, to precarious but stable.
Aftermath
The French success had caught other European powers by surprise, but was now met by open hostility. Dutch diplomats quickly began to establish a coalition against France with Prussia, Spain and Emperor Leopold of the Holy Roman Empire.
In the meanwhile, the French army began to suffer attrition. Half the French invading force was lost during the winter of 1672-3, when they drowned while attempting to cross the half frozen Dutch water line. At the start of 1673, the English parliament was getting weary of continuing the war, eventually settling for peace after the Dutch defeated the combined Anglo-French fleet off the Dutch coast in August of that year. Peace between the French and Dutch was eventually signed in 1678, with the Dutch Republic claiming a near status quo antebellum.
The following decade would see the Dutch Republic foment a revolution in England, with a Dutchman, William III, taking the English Throne, and being at the heart and main monetary backer of every anti-French coalition well into the 18th century.
Sources:
The Miracle of the House of Brandenburg
After several early victories at the battles of Lobositz (1756), Prague (1757), Rossbach (1757) and Leuthen (1757) in the 7 years war, Frederick the Great of Prussia was increasingly a David fighting Goliath.
A coalition of Austria, France, Russia, Sweden and the Holy Roman Empire were all arrayed against the forces of Prussia (and the British satellites of Hanover, Brunswick and Hesse), and the losses incurred from the successive victories had severely dented the quality of the Prussian army.
Frederick had gambled that decisively seizing the German province of Silesia from Austria-Hungary would force them out of the war, but Queen Maria-Theresa was committed to recovering the province before concluding peace. Over the next 5 years, Prussia was forced onto the defensive, repelling successive hammer-blows by her much more numerous opposition.
Suddenly, disaster struck. The victory of the British in North America and India led to the cessation of subsidies to keep Prussia fighting (what now, was the point?). This sudden abandonment by her only ally led Frederick to write to diplomat Von Finckenstein: "We ought now to think of preserving for my nephew [heir], by way of negotiation, whatever fragments of my territory we can save from the avidity of my enemies". The Russian steamroller was gathering pace towards Prussian territories, and it seemed like the end was in sight.
Then, in January 1762, a miracle happened. The Empress of all the Russias suddenly died, leaving her throne to the Prussiophile Peter III - a man who latter expressed to Frederick that he "would rather be a general in the Prussian army than Tsar of Russia". One of Peter's first diplomatic missions was to obtain noble titles from Prussia - naturally agreeing, this charm offensive by Frederick led to Russia dropping out of the war and even giving men to help fight their former allies! Such cool treachery led to Sweden quickly concluding peace, and with France licking her wounds sustained in the Americas and India, Frederick was able to fight Austria-Hungary to a stalemate - finally knocking them out of the war in the Treaty of Hubertusburg in 1763.
This final victory preserved Prussian territorial integrity - including the newly won Silesia. However, it came at a high price. The finances of Prussia were ruined, and the Prussian army - long considered the best in Europe, were a hollow shell of their former selves. They would not recover for 40 years, until after the defeats at Jena and Auerstadt against Napoleon forced reform.
Sources:
Anderson, Fred (2001). Crucible of War: The Seven Years' War and the Fate of Empire in British North America, 1754–1766.
Asprey, Robert B. (1986). Frederick the Great: The Magnificent Enigma.
Fraser, David (2001). Frederick the Great: King of Prussia.
If the movies are about a common soldier in the Napoleonic Wars, many battles may felt like it. Also Bernnadotte rise as King, is one of the moment that surly fit the bill.
Archduke Charles, generalismo of Hapsburg, suprised Napoleon in one of the few battles, where Napoleon was outnumbered. The French army were still veterans compared to the newly reformed Austrian army. In a key moment, the Austrian centre lines broke due to French charges. Another French victory is within reach.
Racing to the front line, Archduke Charles raised the standard banner of Austrian corps. The troops rallied, the French unable to attack effectively again. By the end, it became one of the bloody battles up to that point in the era and Napoleon first major defeat in over a decade. That is the only time in the campaign where Charles was in the front line risking his own life. No one expected it.
Napoleon sent two marshals: Ney and Oudinot, two brave men who despised each others, to attack Berlin. At Dennewitz, they fought a gruelling battle with the Prussian army under general Bulow. At its climax, there is a rainstorm, that increased the attack of the Prussian. As their organization crumbling under pressure, Ney former mentor and personal friend, Bernadotte arrived with an army at his flank, sent a horse artillery unit to blast and finish the French army. The French retreat, Bernadotte rest his troops who almost did not do any fighting, and the Prussian' s generals are angry.
It took Bernadotte 6.5 hours to march 15 miles in this battle. 7 years ago, he was a legend in chasing and crush the Prussian army across Germany in quick successions, inflicting many casuality and took many prisoners. Bernadotte with his usual bragging made a proclamation praising his troops arrivals for being the decisive factor in the battle. The French lost 10000 men, the Prussian 7000 and the Swedes under Bernadotte: 0.
That one is a movie on its own. After Wagram (1809), Napoleon is finding ways to kick him upstair. Bernadotte series of bragging high, deliver low (by Napoleon' s expectations) resulted in him sitting around without a proper responsibilities. Then a Swedish delegate came asking if he want to be ruler of Swede in 1810.
The issues is more complicated and full of lucky accidents. A series of proper heirs is dead or unavailable for different reason. The Swedish delegate actually acted on his own, he want the guy who took his uncle as war prisoner and he got arrested for defying royal orders when he arrived home. Basically, this guy who is about to be forced to retired from political and military career, coming after the most bloody of his life, suddenly was given a royal title from a country he never visit, because of a bunch of war prisoners he took years before.
Instead of being known as one of Napoleon' s worst marshal as his records in Napoleon' s command may indicated, he became the founder of the dynasty that rule Sweden today. The story of Norway-Swedish also had similar elements. While he was in Norway in Novemver 1814, to establish the new constitution after a short war. A fire broke out in Oslo. Bernadotte who arrived there with son without a company of Swedish Guards, show his classic organization skills and he left Norway a very popular monarch.
Sources:
John Hill. 1809 Thunder on the Danube: Napoleon Defeat of the Hapsburg Vol 2.
Alan Palmer. Bernadotte: Napoleon' s Marshal, Sweden' s King.
You can check out this previous answer from u/kallipolan to learn about the two Mongol invasions of Japan that were thwarted, in part, by storms: