The Battle of Isaszeg (6 April 1849) took place in the Spring Campaign of the Hungarian War of Independence from 1848 to 1849, between the Austrian Empire and the Hungarian Revolutionary Army supplemented by Polish volunteers. The Austrian forces were led by Field Marshal Alfred I, Prince of Windisch-Grätz and the Hungarians by General Artúr Görgei. The battle was one of the turning points of the Hungarian War of Independence, being the decisive engagement of the so-called Gödöllő operation, and closing the first phase of the Spring Campaign.

This battle was the first battle between the Hungarian and the Habsburg main armies after the Battle of Kápolna, the Hungarian revolutionary army proving that they can beat the main army of one of the most powerful empires of the time. The Hungarian victory precipitated a series of setbacks to the Habsburg Imperial Armies in April–May 1849, forcing them to retreat from occupied central and western Hungary, towards the western border, opening the way towards Pest-Buda and Komárom, and convincing the Hungarian National Assembly to issue the Hungarian Declaration of Independence (from the Habsburg Dynasty). Windisch-Grätz was dismissed from the leadership of the Imperial forces in Hungary on 12 April 1849, six days after the defeat.

Background

After the Battle of Kápolna (26–27 February 1849), the commander of the Austrian imperial forces, Alfred I, Prince of Windisch-Grätz, thought that he had destroyed the Hungarian revolutionaries once and for all. In his report of 3 March sent to the imperial court in Olmütz, he wrote: "I smashed the rebel hordes, and in a few days I will be in Debrecen" (the temporary capital of Hungary).. Despite this he did not attack the Hungarian forces, as he lacked reliable information about the numbers facing him if he crossed the Tisza river and because of his caution, lost the opportunity to win the war. While he was deciding whether to attack or not, the Hungarian commanders, who were discontented with the disappointing performance of Lieutenant General Henryk Dembiński as high commander of the Hungarian forces, blamed him for losing the Battle of Kápolna, had started a "rebellion". At a meeting in Tiszafüred, they forced the Government Commissioner Bertalan Szemere to depose the Polish general and put Artúr Görgei in command. This so infuriated Lajos Kossuth, the President of the National Defense Committee (the interim government of Hungary), that he wanted to execute Görgei for rebellion. Finally, he was persuaded by the support of the Hungarian generals for Görgei to change his mind and accept the removal of Dembiński, although his dislike of Görgei prevented him from accepting Szemere's choice of successor and he named Lieutenant General Antal Vetter high commander instead. But Vetter became ill on 28 March, and after two days, Kossuth was forced to accept Görgei as temporary high commander of the Hungarian main forces..

Windisch-Grätz's uncertainty was amplified by diversionary Hungarian attacks: in the south at the Battle of Szolnok on 5 March, and in the north, where on 24 March the 800-strong commando of Major Lajos Beniczky attacked an Imperial detachment under Colonel Károly Almásy at Losonc. Half of Almásy's soldiers were captured, and Almásy reported to Windisch-Grätz that he had been attacked by a 6,000-strong army. Because of this, the Austrian marshal scattered his troops in all directions to prevent a surprise attack. His main concern was a maneuver to bypass his northern flank, which he feared would raise the siege of the fortress of Komárom and cut his supply lines..

On 30–31 March plans were made for a Hungarian Spring Campaign, led by General Görgei, to liberate the occupied Hungarian lands which lay to the west of the Tisza river, consisting of most of the territory of the Kingdom of Hungary. The Hungarian forces numbered some 47,500 soldiers and 198 guns, organised in four corps led by Generals György Klapka (I Corps), Lajos Aulich (II Corps), János Damjanich (III Corps) and András Gáspár (VII Corps). Windisch-Grätz had 55,000 soldiers and 214 guns and rockets, formed in three corps: I Corps (Lieutenant Field Marshal Josip Jelačić), II Corps (Lieutenant General Anton Csorich), and III Corps (General Franz Schlik), and an additional division (Lieutenant General Georg Heinrich Ramberg)..

The Hungarian plan, elaborated by Antal Vetter, was for VII Corps to divert the attention of Windisch-Grätz by attacking from the direction of Hatvan, while I, II, and III corps encircled the Austrian forces from the south-west, cutting them off from the capital cities (Pest and Buda). According to the plan, the VII corps had to stay at Hatvan until 5 April and then reach Bag the following day. The attack on the Austrian forces had to occur from two directions at Gödöllő on 7 April, while the I Corps advanced to Kerepes and fell on the Austrians from behind, preventing them from retreating towards Pest. The key to the plan was for the Austrians not to discover the Hungarian troop movements until their encirclement was complete.

Prelude On 2 April, the preliminary fighting began when the VII Corps clashed with the Austrian III Corps at the Battle of Hatvan. Schlik had wanted to obtain information for Windisch-Grätz about the positions and numbers of the Hungarian army and had moved towards Hatvan but was defeated there by the VII Corps and forced to withdraw without accomplishing his purpose. Windisch-Grätz assumed that Schlik had come up against the main Hungarian army and remained ignorant of the true whereabouts of the Hungarian army.. The other three Hungarian corps moved south-west as planned and on 4 April met and defeated the Austrian I Corps at the Battle of Tápióbicske. Although Klapka's attack at Tápióbicske had revealed where the Hungarian troops really were, Görgei decided to continue with the plan..

After the fighting on 4 April, Jelačić, the Ban of Croatia, claimed to Windisch-Grätz that he had actually been victorious, which misled the Field Marshal into ordering him to pursue the Hungarians. Rather than fleeing, the Hungarians were closing in on Windisch-Grätz's headquarters at Gödöllő, even as he was planning an attack on them for the following morning.. On 5 April he sent two companies of lancers, two companies of light horse and two rockets under the command of Lieutenant General Franz Liechtenstein on a reconnaissance mission to Hatvan.. After a skirmish with four companies of Hungarian hussars, in which the Hungarians retreated, Windisch-Grätz started to suspect that at Hatvan station smaller Hungarian forces, but instead of sending superior forces to defeat them, and push towards Debrecen, or to gather all his forces around Gödöllő, he did quite the opposite.Bánlaky József: Lovas összeütközés Hatvan előtt. 1849. április 5-én. A magyar nemzet hadtörténete XXI Arcanum Adatbázis Kft. 2001 Fearing that the Hungarian main forces would get around him from the south and cut his lines to the capital, or from the north and liberate the fortress of Komárom from the Austrian siege, he sent the Austrian III Corps to Gödöllő and I Corps southwards to Isaszeg. Two brigades of the Austrian II Corps were also sent to Vác, and Lieutenant General Georg Heinrich Ramberg ordered to join him with his brigade; two brigades remained in Pest.. Windisch-Grätz had scattered his forces over , too far apart for mutual support.

Although the Hungarian front line was only -long, Görgei could only deploy two-thirds of his troops at any point in the battle because of his orders to his generals regarding their movements prior to the attack on 7 April, the day the battle was to begin. His orders to his corps and units in what direction to march that day, were influenced by his belief that the Austrian troops are still along the Galga line: the VII. corps had to move towards Aszód, reach the Galga, and occupy Bag; the I. corps from Süly towards Isaszeg (marching on the ridge which stretches between the two localities), sending the brigade from its left wing to Pécel; the III. corps, with maximum precautions, had to advance from Tápiószecső through Kóka and Királyerdő towards Isaszeg, sending detachments to occupy the Szent László and Szentkirály farms; and II Corps had orders to take up a position at Dány and occupy with a strong detachment Zsámbok.Bánlaky József: Az isaszegi csata (1849. április 6-án). A magyar nemzet hadtörténete XXI Arcanum Adatbázis Kft. 2001 He would be in Kóka, from Isaszeg.. Görgei's plan was for Gáspár to pin with the VII. corps, the Austrian left wing while the other three corps (I., II., III.) attacked their right flank at Isaszeg. This would push the Austrians northwards from Pest, enabling the liberation of the Hungarian capital on the Eastern bank of the Danube. This forced a dilemma on Windisch-Grätz, to accept a battle where the Hungarians had superiority or to retreat to Pest, which was hard to defend, being open to attacks from three directions. It also had only one unfinished bridge (the Chain Bridge), to allow his troops to cross the Danube to Buda on the other side, should he need to retreat, which would have been impossible. Windisch-Grätz chose the lesser of two evils..

The Field Marshal wrote on 5 April at 5:00 p.m. to Jelačić that he retreats his troops to Isaszeg, because he was informed that Hungarian troops are advancing from the south towards Pest.

Opposing forces :

- I. corps:

Máriássy infantry division: Dipold infantry brigade: 17 infantry companies, 8 cannons = 2475 soldiers; Bobich infantry brigade: 18 infantry companies, 6 cannons = 3129 soldiers; Kazinczy infantry division: Bátori-Sulcz infantry brigade: 18 infantry companies, 8 cannons = 2086 soldiers; Zákó infantry brigade: 6 infantry companies, 8 cannons = 1052 soldiers; Dessewffy cavalry brigade: 16 cavalry companies = 2085 soldiers

10,827 soldiers (59 infantry companies, 16 cavalry companies), 30 cannons.

- II. corps:

Hertelendy combined division: Patay infantry brigade: 20 infantry companies, 14 cannons = 3028 soldiers; Mándy cavalry brigade: 9 cavalry companies, 8 cannons = 3129 soldiers; Szekulits infantry division: Mihály infantry brigade: 15 infantry companies, 6 cannons = 2202 soldiers; Buttler infantry brigade: 12 infantry companies, 8 cannons = 2515 soldiers;

8896 soldiers (47 infantry companies, 9 cavalry companies), 36 cannons.

- III. corps:

Knezich infantry division: Kiss infantry brigade: 16 infantry companies, 8 cannons = 2658 soldiers; Kökényessy infantry brigade: 15 infantry companies, 3 cannons = 2511 soldiers; Wysocki infantry division: Leiningen infantry brigade: 12 infantry companies, 8 cannons = 1772 soldiers; Czillich infantry brigade: 16 infantry companies, 8 cannons = 2373 soldiers; Kászonyi cavalry brigade: 16 cavalry companies, 6 cannons = 2278 soldiers;

11,592 soldiers (59 infantry companies, 16 cavalry companies), 33 cannons..

- VII. corps:

1. (Gáspár) division: Horváth brigade: 39. infantry battalion, 6 companies of the 9. (Nicholas) hussar regiment, 2. six pounder cavalry battery; Waldberg brigade: 1. battalion of the 60. (Wasa) infantry regiment, 4. six pounder infantry battery; Petheő brigade: Nógrád battalion, 2 companies of the Újház jägers, 2 sapper companies, the Pozsony six pounder battery;. 2. (Kmety) division: Gergely brigade: 10. infantry battalion, 23. infantry battalion, 1 sapper company, 3. six pounder infantry battery; Újváry brigade: 45. infantry battalion, 2 companies of jägers, 4 companies of the 9. (Wilhelm) hussar regiment, 4. six pounder cavalry battery; Üchritz brigade: 33. infantry battalion, 2. infantry battalion from Besztercebánya, 2 companies of the 12. (Nádor) hussar regiment, 5. six pounder cavalry battery; 3. (Poeltenberg) division: Kossuth brigade: 1. infantry battalion, 1. infantry battalion from Besztercebánya, 2 companies of the 4. (Alexander) hussar regiment, 5. six pounder infantry battery;