Benedek was born in Sopron as the son of a physician. He was trained at the Theresiana Military Academy in Vienna, from which he graduated seventh in his class. In 1822, he was assigned to the 27th infantry regiment of the Austrian Imperial Army. He was made a First Lieutenant in 1833, and was assigned to the Quartermaster - General. In 1835, he was promoted to the rank of Captain.

In 1840 Benedek was made a Major and aide to the General Commander of Galicia. While still serving in Galicia he was again promoted to Lieutenant - Colonel in 1843. For suppressing an uprising in the town of Gdow in 1846 he was awarded the Knight's Cross of the Order of Leopold as well as given the rank of Colonel.

In August 1847, Benedek was entrusted with the command of the 33rd infantry regiment in Italy. On 5 April 1848 he took over the command of a newly formed brigade that consisted of two battalions. This brigade saw battle in the first Italian war of independence several times, notably at Curtatone in 1848. The following day, Benedek led his troops in the Battle of Goito.

Benedek was afterwards awarded the Commanders' Cross of the Order of Leopold, and the Knight's Cross of the Military Order of Maria Theresa. This officially made Benedek a knight (hence Ludwig, Ritter von Benedek). On April 3, 1849, he became Major General and was appointed to the staff of the Chief of Quartermaster - General with the 2nd Army in Italy.

In 1849, Benedek was sent to Hungary. Leading troops in the Battle of Győr, he was instrumental in striking down the rebellion. At another battle in Szőny he was seriously wounded. He was given the Military Merit Cross and made Regimental Colonel. Benedek was made Chief of Staff to Radetzky in Italy.

He was promoted to Feldmarschallleutnant in 1852 and, when Radetzky retired in 1857, Benedek became the Commander of the II Army Corps.

In early 1859, Benedek was Commander General of the VIII th army corps in the Second Italian War of Independence. On 27 May 1859, he was promoted to the rank of Feldzeugmeister, second in command of the entire Austrian Army. On 24 June, under the command of the young Emperor Franz Joseph I, he fought in the Battle of Solferino against the French troops of the Emperor Napoleon III.

Benedek was attacked on the right flank by the entire army of King Victor Emmanuel II of Piedmont - Sardinia, just a few kilometers north of Solferino in the Battle of San Martino. The Austrian units threw the Piedmontese back at first and were able to hold their ground. In the meantime Franz Joseph was defeated at Solferino and Benedek aided his retreat to San Martino. Benedek received the Commander's Cross of the Military Order of Maria Theresa in 1859.

After the Austrian defeat, Benedek was appointed Chief of the General Quartermaster Staff on January 31, 1860, and to the Governorship of Hungary in April.

On October 20, 1860, Benedek assumed command of the Austrian forces in Lombardy - Venetia, Carinthia, Carniola, the Tyrol and the Adriatic Coastland and was awarded the Grand Cross of the Order of Leopold with War Decoration on January 14, 1862.

Benedek was a staunch believer in the concept that the army was the chief guardian of the Habsburg monarchy and needed to protect it from liberal and nationalist forces; loyalty to the dynasty and monarch were paramount and suspicion of the civilian professional and business classes followed. In a circular to his officers in March 1861 he warned against "international revolutionaries, lawyers and doctors without practices, ambitious and money hungry journalists, dissatisfied professors and schoolteachers" as well as "debt ridden nobles and cowardly magnates" who threatened the monarchy. A year later he further stated in Verona that the army's purpose was "to serve, fight, and if necessary die with honor for the emperor and supreme warlord." Benedek believed in a traditional concept of war where valor and courage were of chief importance, where "simple rules" were superior to "complicated calculations". Following in this vein, he opposed the notion of a national, Prussian style general staff of officers selected for their education and intellect.

At the outbreak of the Austro - Prussian War in 1866, Benedek was made the Commander in Chief of the Northern Army. He had previously declined the appointment three times, claiming that he knew neither the terrain in the north nor the enemy. Delaying his departure from Verona for nearly two months, he arrived in Vienna only on May 12 and did not establish his headquarters at Olmütz (Olomouc) until May 26. Furthermore, his two chiefs of staff, von Krismanić and von Henikstein, encouraged his pessimism and reluctance to engage the enemy.

While the Prussians advanced against and defeated Austria's German allies (Hanover, Hesse - Kassel, and Saxony), Benedek remained in a defensive posture. Urged by Emperor Franz Joseph's emissary, Lieutenant Colonel Friedrich Beck, to advance, Benedek and his staff replied the army was still not ready. Concerning himself with issues of military dress and ceremony and emphasizing the importance of close combat in the coming battles (despite the superiority of the Prussians' needle guns), Benedek only deployed his troops at the end of June. Marching in three columns, they took up defensive positions near the fortress of Josefstadt and the Saxon and Silesian mountain passes.

When the Prussians crossed into Bohemia, Benedek failed to mass his forces against the separate enemy formations and suffered defeats across his front (except for a costly stand at Trautenau). Despite ordering a change of tactics and suddenly admitting the importance of artillery fire prior to the bayonet charge, morale among both the leadership and soldiers was shaken, and Benedek ordered his troops back to Olmütz. Stating that a "catastrophe" was at hand, he pleaded with the emperor to make peace with Prussia. When this was refused, he drew up his army in a defensive position against the Elbe between Sadowa and Königgrätz.

When on July 3, 1866, the Prussians attacked, Benedek had a numerical advantage. Yet he expected to face only the Prussian First Army, and the arrival of the Prussian Second Army under Crown Prince Frederick William, attacking the Austrian flank at Chlum, disrupted the Austrian lines. Benedek ordered a retreat and crossed the river himself in the evening and informed the emperor that the catastrophe he had feared had indeed taken place. He offered to rally again at Olmütz but the retreat became a near rout. On July 10, Archduke Albrecht was appointed commander of all armies and established defenses around Vienna. However, the Prussians had achieved their objectives and were suffering a cholera outbreak while the Austrians were desperate for an end to the fight; an armistice was signed on July 21.

This placed Emperor Franz Joseph I in a difficult position. There was extensive demand for the blame for the defeat to be placed on Benedek. He resigned as Commander - in - Chief at Pressburg (Bratislava) on July 26, 1866. The highest military law senate imposed a court martial against him and was to investigate of the battle. This was stopped by the instruction of the emperor. Benedek was ordered never to speak about the circumstances of the defeat. When a scathing article in the Wiener Zeitung on December 8, 1866 blamed him alone for the catastrophe, he had no right to reply.

The former first soldier of the Empire lived for another fifteen years in quiet retirement at Graz, and died there on April 27, 1881.