Construction and delivery

A torpedo being loaded into Xifias at Toulon

The Hellenic Navy underwent a major reorganization and rearmament in the aftermath of the 1909 Goudi coup. The putschists pressured the Greek government into ordering submersibles (as submarines were known at the time). Thus submersible Delfin and her sister ship Xifias were ordered from the Schneider Shipyards at Chalon-sur-Saône, France in September 1910. Delfin was named after Greek word for dolphin. Construction of Delfin had begun in early 1909, before the Greek order was placed, based on the design of naval architect Maxime Laubeuf.^[6][7]

Construction was completed on 11 November 1911, limited trials were conducted at the port as the installation of the ship's equipment continued. The early trials were supervised by Lieutenant Commander Stefanos Paparrigopoulos and seven other Greek officers. Basic trials and equipment installation was completed on 11 January 1912, Delfin was then transported by barges to the Schneider trial station at St. Mandrier, near Toulon. Considerable time delays in carrying out sea trials and equipment checks led to the postponement of the commissioning until 9 August 1912. A few days later maximum depth trials were performed with the ship diving to 36 m (118 ft). During the course of August and September the ship's crew underwent intense training under the guidance of French officers specializing in submersibles. Most of the training dives took place on a French submarine rather than Delfin itself. As tensions between Greece and the Ottoman Empire escalated the decision was taken for Delfin to depart for Greece before her crew's training had been completed.^[8][9] Delfin sailed for Greece on 29 September, the ship traveled on the surface and unescorted, arriving on Corfu on 4 October to repair damage to her left engine. She reached her destination the Port of Piraeus the following day, where she was welcomed by the commander of the British naval mission Rear Admiral Lionel Grant Tufnell, the Minister of Naval Affairs Nikolaos Stratos and the Finance Minister Alexandros Diomidis. The same day Greece declared war against the Ottomans, joining the rest of the Balkan League in the First Balkan War.^[10][11] This unescorted, non-stop journey of 1,100 mi (1,800 km) 1,100 miles set a world record and confirmed the abilities of her crew, despite their limited training. However, it also meant that no reserve crew could be trained, limiting her battle effectiveness due to the crew's fatigue.^[12] Moreover the Salamis Naval Base did not have the necessary technical facilities to service this new type of ship.^[10] It possessed neither specialized workshops nor separate power generators and compressors to address the needs of the ships. ^[13] Delfin was the first submarine to enter the service of the Greek navy. ^[14] Nordenfelt I which had been ordered in 1884, had disappointed the Greek authorities during its trials in early 1886 and its purchase was subsequently cancelled. Its hull was abandoned in Piraeus.^[15]

Balkan Wars

On 19 October, Delfin departed from Salamis and sailed parallel to Euboea towards the island of Skiathos. In Skiathos she was joined by the merchant ship Kanaris which was supposed to serve as the submarine's refueling ship but in reality she had no such capabilities. Delphin's crew thus simply slept on Kanaris. Following the Capture of Lemnos, the Greek fleet relocated to Moudros Bay. At Moudros, Delfin's crew underwent intensive training dives and carried out regular equipment inspections but no attack training due to logistical constraints. On 20 November, Delfin was transferred to Tenedos. A day later she began daily conducting day time offensive patrols (both submerged and on the surface) at a distance of 4,000–6,000 meters (13,000–20,000 ft) from the Ottoman forts guarding the entrance to the Dardanelles. Those were the first offensive patrols in the history of submarine warfare.^[16] At night Delfin anchored at Tenedos where her crew rested and carried out maintenance works.^[17]

The patrols were uneventful, until December when the Ottomans decided to intensify their naval operations, in view of the failed peace negotiations with Greece. On the morning of 1 December, an Ottoman destroyer emerged from the straights, coming under fire from two Greek ships. However, the commander of the Destroyers Captain Ioannis Vratsanos initially ordered Delfin to remain in port. At 13:26 p.m. Delfin's captain was informed that the Ottoman light cruiser Mecidiye had appeared in front of the straits. The submarine departed Tenedos at 13:26 p.m. and dove 12 minutes later, but arrived too late to intercept Mecidiye. On 3 December, the submarine was conducting an early morning patrol, at 8:10 a.m. she received information that the Ottomans began assembling in front of the Dardanelles. By 8:50 a.m. the entire Ottoman fleet appeared in front of the straits. Once again Delfin is ordered to stand by, at 9:22 a.m. the Ottomans opened fire marking the beginning of the Battle of Elli. Two minutes earlier Delfin sailed submerged in battle order towards the enemy. Strong sea currents prevented Delfin from engaging the enemy, as the Ottomans turned back at full speed after a brief engagement. Commanding officer Stefanos Paparrigopoulos sent a second strongly worded complaint to the fleet commander Pavlos Kountouriotis explaining that the stand by orders had made the submarine's successful operation untenable. On 5 December, Kountouriotis granted Paparrigopoulos complete freedom of action.^[18]

On the morning of 9 December, Delfin was approaching the port of Tenedos in order to charge her batteries when she received information about Mecidiye and five Ottoman destroyers were located outside the straits. Despite the fact that the batteries were at half of their capacity, Delfin sailed at full speed towards the island of Mavria and halted there. At 9:05 a.m. she was notified that the Ottoman ships had been seen on the western tip of Imbros. She submerged at 9:52 a.m., during the course of the dive the submarine took a negative longitudinal tilt of at least 20 degrees. The blasting of all her ballast tanks brought her back to the surface. Paparrigopoulos ordered a repeat dive which was carried out successfully. Delfin dove to periscope depth and spotted Mecidiye, Berk-i Satvet and four Ottoman destroyers sailing straight towards their estimated course in preparation for the attack. At either 10:30 a.m.^[19] or 10:40 a.m., upon approaching the enemy undetected at a distance of either 800 metres (2,600 ft)^[20][21] or 500 metres (1,600 ft) Delfin fired her bow torpedo at Mecidiye. The torpedo made some jumps on the sea surface disappeared from view, presumably having sunk without impacting its target. This marked the first submerged torpedo attack in naval history. The splash of the ejection and the torpedo itself came into view of the Ottomans, who maneuvered their ships towards Delfin at full speed. She dove to 18 metres (59 ft) and turned away from the enemy, at 10:55 a.m. she returned to periscope depth having evaded her pursuers.^[22]

At 11:40 a.m., the submarine ran aground on the Shimal reef north of Tenedos. Having failed to blast her ballast tanks with the remaining small volume of air, the decision was taken to drop her safety leads; enabling her to resurface. Delfin returned to the Bay of Mudros and after two days sailed for the Salamis Naval Base. She took no further part in offensive military operations during the war, as she was unable to submerge without her lead ballast.^[23][24] There she was placed in a dry dock and refitted with a new lead ballast. In January 1913, Delfin began patrolling the Saronic Gulf in order to protect military transport ships from a possible attack by the Ottoman cruiser Hamidiye. Those lasted until spring, when Hamidiye departed for the Red Sea.^[25]

Later service

During the course of World War I, Greece was affected by the National Schism political crisis. The crux of the dispute was on whether the country should remain neutral or join the war on the side of the Entente. The Entente intervened into Greek affairs numerous times in an effort to support the pro-war Provisional Government of National Defence, including a blockade of Piraeus and the Salamis Naval Base.^[26]

On 28 September 1916, two steamboats from the British battleship HMS Duncan towed Delfin to Adamantas on the island of Milos where they were placed under the supervision of the French Navy. The submersible remained at Adamantas until September 1917, when she was towed back to Salamis Naval Base and officially returned back to the Greek Navy on 14 October. During the period of her captivity she remained exposed to the elements and received no maintenance. As a result, the condition of her equipment had eroded, while the plaques of her batteries had been irreparably damaged. New plaques were ordered from France, but those arrived only at the end of the year and many of them bore traces of sea water contamination. Systematic repairs of the plaques led to the assembly of a single battery which was placed on Xifias. In April 1919, the battery was removed from Xifias and placed into Delfin after the steel plates of the former began detaching. Delfin resumed operation on 20 May and remained in service until 23 July 1919, when maneuvers were halted due to the corrosion of the ballast tanks.^[27]

The poor condition of the steel plates and ballast tanks of the submersibles along with the absence of radios and gyrocompasses led to their decommissioning in early 1920. One of the periscopes and some of the electric motors were used for training purposes in the Hellenic Naval Academy, while the pressure hulls were sold to the Port of Piraeus Authority.^[28]