Siege of La Rochelle ( 1572 – 73 ) The Siege of La Rochelle of 1572 – 1573 was a massive military assault on the Huguenot - held city of La Rochelle by Catholic troops during the fourth phase of the French Wars of Religion , following the August 1572 St . Bartholomew ' s Day massacre . The conflict began in November 1572 when inhabitants of the city refused to receive Armand de Gontaut , baron de Biron as royal governor . Beginning 11 February 1573 , the siege was led by the Duke of Anjou ( the future Henry III ) . Political considerations following the duke ' s election to the throne of Poland in May 1573 resulted in negotiations , culminating on 24 June 1573 , that lifted the siege on 6 July 1573 . The Edict of Boulogne signed shortly thereafter brought an end to this phase of the civil war . The siege of La Rochelle was contemporaneous with Catholic assaults on the cities of Sommières ( led by Henri I de Montmorency ) and Sancerre . Background . Since 1568 , La Rochelle had been the main base of the Huguenots in France . A city of 20 , 000 inhabitants and a port of strategic importance with historic links to England , La Rochelle benefited from administrative autonomy ( lack of seigneur , bishop or parlement ) and had become overwhelmingly Huguenot ( Calvinist ) . As soon as 1571 , the Royal fleet was more or less blockading the city , led by Captain Polin and Filippo di Piero Strozzi . After the St . Bartholomew ' s Day massacre and other massacres across France in the fall of 1572 , numerous Huguenots fled to the city La Rochelle as a last refuge . The city was well fortified , with access to the sea . The Siege . The conflict started in November 1572 when inhabitants of the city refused to receive Armand de Gontaut , baron de Biron as royal governor . Charles IX ordered the city to be sieged . In the middle of November , François de la Noue , sent by Charles IX to negotiate with the city , was invited by the inhabitants to take up their defense . With the king ' s acceptance , La Noue joined the assieged city , but was unable to effect a solution to the crisis , and on 12 March 1573 he left the city , to watch the subsequent events from the royal camp . On 11 February 1573 , the Duke of Anjou arrived to take command of the siege with 28 , 000 men . His massive resources – munitions , cannons , gunpowder , cannonballs , food – were gathered from Paris , Picardy , Normandy , Poitou , Saintonge and Angoumois . The army included the Duke ' s brother François d ' Alençon ; the two former leaders of the Huguenots , Henry of Navarre and Henri I de Bourbon , prince de Condé ( both recently converted to Catholicism ) ; members of the Guise family , Charles of Lorraine , Duke of Mayenne , Claude , Duke of Aumale ( killed on 21 February ) , Henry I , Duke of Guise ; and other nobles including : Louis IV de Nevers , Guillaume de Thoré , Henri de la Tour d ' Auvergne , Filippo di Piero Strozzi , Albert de Gondi , Blaise de Monluc , Artus de Cossé - Brissac , Pierre de Bourdeille , seigneur de Brantôme , Armand de Gontaut . Among these nobles were some who remain suspicious of the present political tact or of the violence of the St . Bartholomew ' s Day massacre , and some who were sympathetic to the Protestant cause ; political intrigues traversed the royal camp . Eight assaults of the city were waged from February to June . These attacks , along with cold winter , resulted in large the losses on the royal army ' s side . ( Brantôme , who participated in the siege , exaggerated the death toll as 22 , 000 men ; records show that of 155 commanders , 66 were killed and 47 were wounded . ) On 26 March 1573 , 150 attackers were killed in an accidental explosion of a mine intended to destroy the ramparts . The Duke of Anjou was himself wounded several times during these conflicts . On 23 May 1573 , 6 , 000 Swiss guard mercenaries arrived as reinforcements to the royal army , but the attack three days later was a disaster for the royal troops . The inhabitants of the city sent an ambassador to Queen Elizabeth I of England seeking her assistance , but Elizabeth – still bound by her 1572 treaty with France ( the Treaty of Blois ( 1572 ) ) – was only able to send a limited number of ships led by Gabriel , comte de Montgomery . Six ships arrived in February 1573 , but a larger group of ships were forced to turn back by the French navy in April 1573 ( retreating to Belle Île and then Jersey ) . The majority of the city ' s dwindling resources were supplied through small naval raids on Catholic ( principally Spanish ) ships ( which were also being attacked by the Dutch " gueux de mer " corsairs ) . To block La Rochelle ' s ships ' access to the sea , the Duke of Nevers sank a large barge , with no effect . ( In the siege of 1627 - 28 , Cardinal Richelieu would construct a massive sea barricade to block the city ) . At the end of May 1573 , Henry of Anjou learned that he had been elected King of Poland , a country with a large Protestant minority , and political considerations forced him to negotiate an end the assault . An agreement was reached on 24 June 1573 and Catholic troops ended the siege on 6 July 1573 . Aftermath . The fourth phase of the Wars of Religion was brought to a close by the Edict of Boulogne signed in July 1573 . La Rochelle was designated as one of the three cities in France where the Protestant faith was permitted , but only under strict conditions .