The Siege of Tsingtao was the attack on the German port of Tsingtao (Qingdao) in China during World War I by Japan and the United Kingdom. It took place between 31 October and 7 November 1914 and was fought by Japan and the United Kingdom against Germany. It was the first encounter between Japanese and German forces and also the first Anglo-Japanese operation during the war.
Throughout the late 19th century, Germany joined other European powers in an imperialist scramble for colonial possessions. As with other world powers, the Germans began to interfere in Chinese local affairs. After two German missionaries were killed in 1897, China was forced to transfer Kiaochow and the surrounding areas in Shantung (now Shandong) to Germany in 1898 on a 99-year lease. The Germans then began to assert their influence across the rest of the province of Shandong and built the city and port of Tsingtao. The port became the home base of the German Navy's East Asia Squadron, which operated in support of German territories in the Pacific.
The British perceived the German presence in China as a threat to their interests and leased Weihaiwei, also in Shantung, as a naval port and coaling station in response, while Russia and France leased their own at Port Arthur (now Lüshunkou) and Kwang-Chou-Wan, respectively. The British also began to forge close ties with the Japanese.
Japan's developments in the late 19th century also mirrored that of other imperialist powers and Japan acquired colonial territories on the Asian mainland. Japanese and British diplomatic relations became progressively closer and an Anglo-Japanese alliance was signed on 30 January 1902. This was seen as a necessity by both powers, especially by Japan, who saw it as a further step to deter Russia and being recognized as a world power. Japan demonstrated its potential of being a rival to the British Empire after its victory in the Russo-Japanese War 1904–1905; the alliance remained intact into World War I.
After the First World War began in early August 1914, Britain soon thereafter requested Japanese assistance.
In accordance with the terms of the Anglo-Japanese alliance, the Japanese Government sided with Britain in the war. On 15 August Japan issued an ultimatum to Germany, stating that Germany must withdraw their warships from Chinese and Japanese waters and transfer control of Tsingtao to Japan. The following day, Major-General Mitsuomi Kamio, General Officer Commanding (GOC), 18th Infantry Division, was directed to begin preparations for an invasion of Tsingtao. When the ultimatum expired on 23 August, Japan declared war on Germany.
At the beginning of hostilities the larger units of the East Asia Squadron under the command of Vice Admiral Maximilian von Spee were dispersed at central Pacific colonies on routine missions. The ships rendezvoused in the northern Marianas for coaling, and, with the exception of SMS Emden which headed for the Indian Ocean, made their way to the west coast of South America. There the squadron destroyed a Royal Navy squadron at the Battle of Coronel before being itself destroyed at the Battle of the Falkland Islands.
The Boxer Rebellion had led the German administration in Tsingtao to more seriously consider the defense of Tsingtao. The port and town were separated from the rest of the peninsula by steep hills. A natural line of defense lay along these hills, from the Kaiserstuhl to Litsuner Heights. The second 17 kilometres (11 mi) long line of defense was built up along a closer line of steep hills. The final line of defense was built along hills 200 metres (660 ft) above the town. A network of trenches, batteries, and other fortifications were built here before the siege.
The Germans also built up their seaward defenses, laying mines on the approaches to the harbour, as well as building four batteries and five redoubts. The fortifications were well equipped (although some were using older Chinese artillery) and well manned.
The Imperial Japanese Navy (IJN) first sent ships under Vice-Admiral Sadakichi Kato, flying his flag in the pre-dreadnought Suwo, to blockade the coast of German-controlled Kiaochow, beginning on 27 August. During the course of naval operations off Tsingtao, the British Royal Navy (RN) attached the China Station's pre-dreadnought HMS Triumph and the destroyer HMS Usk to the IJN. The British warships were integrated into the Second Squadron with few problems. According to a German press report following the siege, the Triumph was damaged by German land batteries. The Japanese squadron consisted of mostly obsolete warships, though it did briefly engage a number of more modern vessels. These included the dreadnoughts Kawachi, Settsu, the battlecruiser Kongō, her sister Hiei, and the seaplane carrier Wakamiya, whose aircraft became the first of its kind in the world to successfully attack land and sea targets. These planes would also take part in another military first: the first night-time bombing raid.
The 18th Infantry Division was the primary Japanese Army formation that took part in the initial landings, numbering some 23,000 soldiers with support from 142 artillery pieces. They began to land on 2 September at Lungkow (now Longkou), Shandong, which was experiencing heavy floods at the time, and later at Laoshan Bay on 18 September, about 29 kilometres (18 mi) east of Tsingtao. China protested Japan's violation of her neutrality but did not interfere in the operations.
The British Government and the other European great powers were concerned about Japanese intentions in the region and decided to send a small symbolic British contingent from Tientsin in an effort to allay their fears. The 1,500-man contingent was commanded by Brigadier-General Nathaniel Walter Barnardiston and consisted of 1,000 soldiers of the 2nd Battalion, The South Wales Borderers; later followed by 500 soldiers of the 36th Sikhs.
The Germans responded to the threat against Tsingtao by concentrating all of their available East Asian troops in the city. Kaiser Wilhelm II made the defense of Tsingtao a top priority, saying that "... it would shame me more to surrender Tsingtao to the Japanese than Berlin to the Russians."
The German garrison, commanded by naval Captain and Governor Alfred Meyer-Waldeck, consisted of the marines of III. Seebataillon, naval personnel, and soldiers (Chinese colonial troops and Austro-Hungarian sailors), for a total strength of 3,625 men. He also had a modest complement of vessels, including the torpedo boat S-90; four small gunboats: the Iltis, Jaguar, Tiger, and Luchs; and the Austro-Hungarian protected cruiser Kaiserin Elisabeth, whose crew was initially divided in two: to man the ship and fight as part of the German land forces.
On 22 August HMS Kennet of the China squadron, under the command of Lieutenant Commander F.A. Russel while routinely monitoring the naval trade routes, encountered and was damaged in action by the German torpedo boat SMS S90, the German gunboat SMS Lauting and a 4-inch shore battery off Tsingtao. She was hit twice from the retreating S90. 
As the Japanese approached his position, the German Commander withdrew his forces from the two outer defensive lines and concentrated his troops on the innermost line of defense along the hills closest to the town.
The Austro-Hungarian cruiser, SMS Kaiserin Elisabeth, was stationed in Tsingtao at the start of the war. On 2 September 1914 the German gunboat Jaguar sank the stranded Japanese Destroyer Shirotaye. On 5 September a Japanese recon plane scouted the port and reported that the Asian German fleet had departed. As a result the Japanese ordered the dreadnought, pre-dreadnought and cruiser to leave the blockade.  The next day, the first air-sea battle in history took place when a Farman seaplane launched by the Wakamiya unsuccessfully attacked the Kaiserin Elisabeth and the Jaguar in Qiaozhou Bay with bombs. On 28 September the Jaguar sank the Japanese cruiser Takashio. Early in the siege, the Kaiserin Elisabeth and German gunboat Jaguar made an unsuccessful sortie against Japanese vessels blockading Tsingao. Later, the cruiser's 15 cm and 4.7 cm guns were removed from the ship and mounted on shore, creating the Batterie Elisabeth. The ship's crew took part in the defense of Tsingtao. On 13 September the advancing Japanese land forces launched a cavalry raid on the German rear-guard at Tsimo, which the German gave up and retreated. Subsequently the Japanese took control of Kiautschou and the Santung railway. Lt. Gen. Kamio considered this the point of no return for his land forces and as the weather became extremely harsh he took no risk and fortified the troops at the town and returned the yet-to-arrive reinforcements, reembarked, and landed at Lau Schan bay.
On 17 October 1914 the torpedo boat S-90 slipped out of Tsingtao harbor and fired a single torpedo which sank the Japanese cruiser Takachiho with the loss of 271 officers and men. S-90 was however unable to run the blockade back to Tsingtao and was scuttled in Chinese waters when the ship ran low on fuel.
The Japanese started shelling the fort and the city on 31 October and began digging parallel lines of trenches, just as they had done at the Siege of Port Arthur nine years earlier. Very large 11 inch howitzers from land, in addition to the firing of the Japanese naval guns, brought the German defences under constant bombardment during the night, the Japanese moving their own trenches further forward under the cover of their artillery. The bombardment continued for seven days, employing around 100 siege guns with 1,200 shells each on the Japanese side. While the Germans were able to use the heavy guns of the port fortifications to attack the landward positions of the Allies, they soon ran out of ammunition.
The Germans were only able to field a single aircraft during the siege flown by Lieutenant Gunther Plüschow (a second airplane flown by Lt. Friedrich Müllerskowsky crashed). The surviving aircraft was used primarily for frequent reconnaissance flights, but Plüschow made several nuisance attacks on the vessels of the blockading squadron by dropping jury-rigged munitions and other available ordnance. He also claimed the downing of a Japanese Farman MF.7. Plüschow flew out from Tsingtao on 6 November 1914 carrying the governor's last dispatches which were forwarded to Berlin through neutral diplomatic channels. On the night of 6 November waves of Japanese infantry attacked the third line of defences and overwhelmed the defenders. The next morning, the German forces, along with their Austro-Hungarian allies, asked for terms.
The Allies took formal possession of the colony on 16 November 1914.
Japanese casualties numbered 236 killed and 1,282 wounded; the British, 12 killed and 53 wounded. The German defenders suffered 199 dead and 504 wounded.
Given that the Germans were able to hold out for nearly two months under a total Anglo-Japanese blockade with sustained artillery barrages and being outnumbered 6:1, gave a morale boost during the siege as well as in defeat. After the surrender, the defeated Germans watched the Japanese as they marched into Tsingtao, but turned their backs on the triumphant British as they marched into town. The German dead were buried at Tsingtao while the remaining troops were transported to prisoner of war camps in Japan. The 4700 German prisoners were treated well and with respect in Japan., such as in Bandō prisoner-of-war camp. 170 prisoners chose to remain in Japan after the closure of camps. The internment of German troops in Japan lasted until the formal signature of the Versailles peace treaty in 1919, but due to technical questions the troops were not repatriated before 1920.