France did not declare war on Austria-Hungary until 12 August 1914, with Britain following suit the next day. Vice Admiral Augustin Boué de Lapeyrère, the commander of Anglo-French naval forces in the Mediterranean was ordered to take the offensive against the Austro-Hungarians. His initial task of protecting French troops moving from North Africa to France had by then been largely completed.
The French navy’s war plans had assumed that it would be fighting both Austria-Hungary and its ally Italy, so it had no plan to fight only Austria-Hungary. An attack on the enemy’s main base at Pola, now Pula in Croatia, was thought to be too risky.
De Lapeyrère decided that a sweep into the Adriatic to relieve the Austro-Hungarians blockade of Montenegro might provoke the enemy’s main battle fleet into coming out to fight. This would give the Allies an opportunity to win a decisive victory.
The Austro-Hungarian fleet was heavily outnumbered by the Allied one, which consisted mostly of French ships, but included a few British cruisers and destroyers. The British Mediterranean Fleet’s battlecruisers were watching the Dardanelles in case the German battlecruiser SMS Goeben and light cruiser SMS Breslau came out. Other British ships had been sent to the Red Sea in case German cruisers attempted to attack troopships heading from India to Egypt.
De Lapeyrère’s plan was to take his main battle fleet, showing no lights, along the Italian coast as far as the latitude of the Austrian base at Cattaro, now Kotor in Montenegro. They would then head towards Cattaro and destroy the Austro-Hungarian blockade force, which would have been driven towards them by a force of light cruisers commanded by the British Rear Admiral Ernest Troubridge.
The trap swung shut on 16 August, but caught only the small and old Austro-Hungarian light cruiser SMS Zenta. It fought gallantly but was overwhelmed and sunk in ten minutes. The action was sufficiently close to the coast that the survivors were able to make the shore. A destroyer escaped.
Unsurprisingly, the Austro-Hungarian fleet did not come out to face an enemy that heavily outnumbered it. Paul Halpern notes that ‘[a] curious feature of many prewar plans was the near total absence of what to do next if the enemy fleet did not come out to do battle.’[1]
The Austro-Hungarian naval plan was to maintain a fleet in being. The Allies were hampered by a lack of bases and the French navy’s shortage of colliers and oilers to fuel a fleet that consumed 5,000 tons of coal and 1,000 tons of oil per day.[2] De Lapeyrère was forced to rotate his ships between the Adriatic and Malta.
[1] P. G. Halpern, A Naval History of World War I (London: UCL Press, 1994), p. 59.
[2] Figures from Ibid.
War and Security 
My Grandfather served on the Zenta, when She went down. POW for the rest of the War
Glad he survived a gallant fight against overwhelming odds.