Henry IV of France had given the Huguenots extensive rights in the Edict of Nantes.

La Rochelle has become the stronghold of the French Huguenots, under its own governance.

It is the center of Huguenot seapower, and the strongest center of resistance against the central government.

La Rochelle is, at this time, the second or third largest city in France with over thirty thousand inhabitants.

The assassination of Henry IV in 1610, and the advent of Louis XIII under the regency of Marie de' Medici, had marked a return to pro-Catholic politics and a weakening of the position of the Protestants.

The Duke Henri de Rohan and his brother Benjamin de Rohan, duc de Soubise, had started to organize Protestant resistance from that time, ultimately exploding into a Huguenot rebellion.

The forces of Louis XIII in 1621, t had besieged and captured Saint-Jean d'Angély, and a Blockade of La Rochelle had been attempted in 1621-1622, leading to the battle of Saint-Martin-de-Ré on October 27, 1622 between the naval forces of La Rochelle and a Royal fleet under Charles de Guise.

An uneasy peace had been concluded with the Treaty of Montpellier, but frustrations remain on both sides.

The Huguenots on January 17, 1625, led by Soubise, launch a second rebellion against King Louis XIII After publishing a manifesto, Soubise invades and occupies the island of Ré, seizing it with three hundred soldiers and one hundred sailors.

Charles, Duke of Guise, organizes a landing in order to recapture the islands, using twenty borrowed Dutch warship as well as seven English ships under Henri II, Duke de Montmorency, grand admiral of France.

The Dutch fleet of twenty warships has been supplied under the terms of the 1624 Franco-Dutch Treaty of Compiègne, and is under the command of Admiral Willem Haultain de Zoete. (It will be withdrawn from French service in February 1626 after a resolution of the States-General in December 1625.)

English king Charles I and the Duke of Buckingham had negotiated with the French regent, Cardinal Richelieu, for English ships to aid Richelieu in his fight against the French Protestants (Huguenots), in return for French aid against the Spanish occupying the Palatinate (the Mansfeld expedition of 1624-25), an agreement which has led to great trouble with the English parliament, which is horrified by the help given to France against the Huguenots.

Seven English ships had been delivered by Captain Pennington after many misgivings, and are employed in the conflict, although they are essentially manned by French crews, as most of the English crews had refused to serve against their coreligionists and had disembarked in Dieppe.

The English ships duly see action against La Rochelle, however.

In an early encounter on July 16, 1625, Soubise manages to blow up the Dutch ship under Vice-Admiral Van Dorp, with a loss of three hundred Dutch sailors.

Montmorency leads his large fleet out of Les Sables d'Olonne in September 1625 and defeats the fleet of La Rochelle, commanded by Jean Guiton and Soubise, in front of Saint-Martin-de-Ré on September 18.

Two elite regiments of royal troops under Toiras are landed on the island, defeating Soubise with his three thousand men.

The island of Ré is invested, forcing Soubise to flee to England with his few remaining ships.

Montmorency thus manages to recover both Ile de Ré and Ile d'Oléron, but the jealousy of Richelieu deprives him of the means of following up these advantages.

The French officer Toiras is named as Governor of the island of Ré, and he starts to reinforce fortifications in view of future attacks, especially at the Fort de La Prée and Saint-Martin-de-Ré.

The conflict clearly shows the dependence of France on foreign navies.

This leads Richelieu to launch ambitious plans for a national fleet.

An English invasion force of one hundred ships and six thousand soldiers under Buckingham’s command invades the island of Ile de Ré at the beach of Sablanceau on July 12, 1627, with the objective of controlling the approaches to La Rochelle, and of encouraging the rebellion in the city.

Buckingham wishes to capture the Fort of La Prée and the fortified city of Saint Martin de Ré.

Toiras fights against the landing from behind the dunes, with a force of twelve hundred infantry and two hundred horsemen, but the English beachhead is maintained, with over twelve officers and one hundred men dead.

During a period of three days during which Buckingham consolidates his beachhead, Toiras takes all the available provisions on the island and fortifies himself in the citadel of Saint Martin with one thousand men.

Buckingham endeavors to establish a siege around the citadel, but things prove difficult.

The English siege engineer had drowned during the landing, the cannons are too few and too small, and disease starts to take its toll on the English troops as autumn arrives.

Requested supplies from England also prove insufficient.

Irish troops numbering two thousand arrive under Sir Ralph Bingley on September 3, 1627.

A small supply fleet under Sir William Beecher arrives with only four hundred raw troops.

A Scottish fleet composed of thirty ships, with five thousand men, was on its way on October 1627, but is broken up by a storm on the coast of Norfolk.

A strong relief fleet under the Earl of Holland will only depart on November 6, 1627; this will prove to be too late.

The French, despite difficulties, manage to run a supply fleet during the night of October 7-8, with twenty-nine ships managing to make it through the English naval blockade on a total of thirty-five.

From the mainland, four thousand additional troops are landed on the southern end of the island on October 20.

The rescue troops are under the Marshal of France Henri de Schomberg.

Buckingham attempts a last desperate attack on Saint Martin on October 27, but it is a failure.

The Saint Martin fortress again proves to be impregnable, and the English ladders turn out to be too short to scale the fortification walls.

Although there are indications that the Saint Martin French garrison is also close to exhaustion, Buckingham finally retreats with his troops towards the northern part of the island, with the objective of embarking at the area of Loix.

He is harassed by pursuing French troops, with heavy casualties.

Altogether, Buckingham loses more than five thousand men in the campaign, out of a force of seven thousand.

This is considered as the opening conflict of the Anglo-French War of 1627-1629, itself a part of the Thirty Years' War.