Battle of Buda ( 1849 ) The Battle of Buda ( ) was a battle at Buda , Kingdom of Hungary during the Hungarian Revolution of 1848 . It was part of the Spring Campaign between 4 and 21 May 1849 and ended with Hungarian victory . Castle . Buda Castle was hardly modern during the Battle of Buda of 1686 , and it was antiquated in 1849 . It had no fortifications against direct attacks , its water defences were outdated and it was easy to fire at the castle from the nearby hills . However , the determined defenders made the attack difficult . Evacuation and occupation . Defence of Buda . During the Winter Campaign Mór Perczel ' s army lost the Battle of Mór against Josip Jelačić . Because of this the Hungarians could not defend the Upper Danube . Perczel disagreed with Antal Vetter ' s and György Klapka ' s campaign plans . He suggested to Lajos Kossuth that the Hungarian forces move to Buda and Pest ( now Budapest , Hungary ) . However the Hungarians didn ' t comply with Perczel ' s wishes , because the enemy looked overwhelming , and the defeat and retreat wore them out . Strategy . The Hungarians could not defend the Upper Danube , but it was possible to defend the Castle . The main target of the Austrian leader Alfred I , Prince of Windisch - Grätz was Buda and Pest , but he got no reinforcements to defend the castle . Renovation of the castle . The Hungarian troops abandoned the castle after evacuating Buda and Pest . Windisch - Grätz asked Heinrich Hentzi to lead the Austrians and also to repair the castle ' s walls and towers , to make the water defences stronger . Von Arthurm put at first 85 cannon on the walls , later increasing them to 92 . Battle . After winning back Komárom the battle at Buda seemed an easy victory for the revolutionaries . The Hungarians approached the castle and occupied the area . Artúr Görgey demanded the Austrians ' surrender and promised fair treatment to those captured . Görgey also promised not to attack the castle from the side facing Pest , but that if Hentzi fired at Pest than he would show no mercy . Additionally , Görgey appealed to Hentzi ' s supposed Magyar sympathies ( Hentzi having been born in Debrecen ) , but Hentzi replied that his loyalty was to the Kaiser . Hentzi ' s response was not as Görgey expected : he told Görgey that if the Hungarians didn ' t stop firing the walls , he would fire at Pest . With this , Görgey started to coordinate the attack . Attack against the water defences . Görgey sent György Kmety to attack the water defences and ordered to raze them , but Kmety could not achieve a definitive result . Furthermore Kmety was injured during the mission . The defeat made clear that it would not be an easy attack . Görgey wrote a letter to Richard Guyon and ordered him to send reinforcements from Komárom . On 6 May Guyon sent 5 cannon , which arrived two days later . During that time Görgey ordered the construction of an artillery battery on ( " Sun Hill " ) , one of the hills in Buda . This was completed on 14 May . During this build - up there were fights between the Hungarians and the Austrians . On 5 May Kmety was moving towards the water defences , but Hentzi started to fire at the Hungarians so they had to withdraw . First attack . On 16 May the Hungarians started to fire at the castle walls and broke through them . Görgey ordered the castle be reconnoitre d to secure an advantage in the impending battle , but this was not successful as the ladders were too short and the hole broken through the walls wasn ' t big enough . Görgey ordered eight groups to continuously distract the enemy during the nights . Final attack . The final attack started at 3am on 21 May , when all cannon opened fire at the castle . The attack was not too easy at first , but later the Hungarians managed to enter the castle . The Hungarians occupied it by 7am and Hentzi died during the battle . In all , 368 Hungarians died and approximately 700 were injured . The Austrians lost 710 men , and 4 , 200 men were taken captive – the entire garrison . Aftermath . The victory was an important part of the Spring Campaign although many people thought that the battle lasted too long , and in defending the castle the victorious Hungarians could not take the attack to the Austrians . The Hungarian leaders did not think it as a waste of time because the previous battles at Buda ( such as those in 1541 and in 1686 ) were either unsuccessful or too long . Since 1992 , the Hungarian Government has celebrated the last day of the battle , 21 May , as National Defence Day ( ) .