Named after King James I of Aragon, Jaime I was built in the early 1910s, though her completion was delayed until 1921 owing to a shortage of materials that resulted from the start of World War I in 1914.

The class was ordered as part of a naval construction program to rebuild the fleet after the losses of the Spanish–American War in the context of closer Spanish relations with Britain and France.

The ships were armed with a main battery of eight 305 mm (12 in) guns and were intended to support the French Navy in the event of a major European war.

Jaime I and the bulk of the fleet remained loyal to the republican government, though her sister Alfonso XIII (by then having been renamed España), fell under rebel control.

The Spanish Republican Navy nevertheless failed to make effective use of its naval superiority and Jaime I did not see significant action apart from bombarding Nationalist positions in North Africa.

After the First Moroccan Crisis strengthened Spain's ties to Britain and France and public support for rearmament increased in its aftermath, the Spanish government came to an agreement with those countries for a plan of mutual defense.

[2] This mounting scheme was chosen in preference to superfiring turrets, as was done in the American South Carolina-class battleships, to save weight and cost.

[3] For defense against torpedo boats, she carried a secondary battery that consisted of twenty 102 mm (4 in) guns mounted individually in casemates along the length of the hull.

She was launched on 21 September 1914, less than two months after the start of World War I. Spain remained neutral during the conflict, but because Britain supplied much of the armament and other building materials, work on Jaime I was considerably delayed.

She conducted sea trials in May 1921, slightly exceeding 20 knots (37 km/h; 23 mph) on speed tests, and work was finally finished on 20 December.

Spain and France planned a major landing at Alhucemas, consisting of some 13,000 soldiers, 11 tanks, and 160 aircraft, to attack the core rebel territory in September.

Both fleets provided gunfire support as the ground forces landed on 8 September; the amphibious assault was a success, and after heavy fighting over the next two years, the Rifian rebels were defeated.

[10] In the final days of the conflict in October 1927, Alfonso XIII, his wife, and a number of generals, including Primo de Rivera, Francisco Franco, Dámaso Berenguer, and Ricardo Burguete, traveled to Morocco to tour the pacified colony.

[11] By the early 1930s, the effects of the Great Depression had spurred significant domestic opposition to the regime of Primo de Rivera, leading to his resignation on 28 January, and ultimately to Alfonso XIII's exile in April 1931.

Immediately thereafter, the government of the Second Spanish Republic began a series of cost-cutting measures to offset the deficits that had been incurred during the Rif War, and as a result, both España and Jaime I were placed in reserve in Ferrol on 15 June.

The ships' crews in Ferrol already knew about the plans by 13 July, and many attended a meeting that day to discuss what course of action they would take if the officer corps joined Franco when he launched the coup.

The crews in Cartagena, including Jaime I, mutinied after their commanders began to join the Nationalists, murdering many of them and ensuring the ships would remain under government control in the Spanish Republican Navy.

In Algeciras, she scored hits with her secondary armament on the Nationalist gunboat Eduardo Dato, which was burned down to the waterline,[21] although she was later repaired and returned to service.

[25] When the Republican ships departed, they left behind two of the submarines and one of the destroyers, and some of Jaime I's secondary guns were dismounted, later to be installed on four fishing boats.

Republican anti-aircraft fire was ineffective and failed to prevent the bombers from making two runs on the ship, dropping around sixty 100 kg (220 lb) bombs in total.