By the end of 1594, certain League members still worked against Henry across the country, but all relied on Spain's support. In January 1595, the king declared war on Spain to show Catholics that Spain was using religion as a cover for an attack on the French state—and to show Protestants that his conversion had not made him a puppet of Spain. Also, he hoped to take the war to Spain and make territorial gain. The conflict mostly consisted of military action aimed at League members, such as the Battle of Fontaine-Française, though the Spanish launched a concerted offensive in 1595, taking Doullens, Cambrai and Le Catelet and in the spring of 1596 capturing Calais by April. Following the Spanish capture of Amiens in March 1597 the French crown laid siege until its surrender in September. With that victory Henry's concerns then turned to the situation in Brittany where he promulgated the Edict of Nantes and sent Bellièvre and Brulart de Sillery to negotiate a peace with Spain. The war was drawn to an official close after the Edict of Nantes, with the Peace of Vervins in May 1598.
Question: How many months did the French crown lay siege at Amiens?
Answer: 6