Why did France fight against Spain in the War of the Quadruple Alliance?

France fought against Spain in the War of the Quadruple Alliance primarily to uphold the international order established by the Treaty of Utrecht (1713), which aimed to maintain the balance of power in Europe.1

Spain, under the influence of Philip V and his wife Elizabeth Farnese, sought to reclaim territories in Italy—specifically Sardinia and Sicily—that had been assigned to Austria and Savoy by the Utrecht treaty. By joining the Quadruple Alliance alongside Britain, the Dutch Republic, and Austria, France acted to prevent Spain from unilaterally altering these terms.1

Additionally, the conflict was fueled by internal tensions within the house of Bourbon. Following the death of Louis XIV, Philip V challenged the legitimacy of the French regent, Philippe, duc d’Orléans, believing he had a superior claim to the regency for the young Louis XV.2