The largest battle the Danes fought in the campaign began when the Danish corps marched (along with l´Allemand's light brigade) towards Rendsborg. The march went very slowly as the roads were muddy and in horrible condition. The Danish vanguard reached Holtsee at about 7 o'clock in the morning, where it stopped and waited for the main force.
As the Danish vanguard were waiting and resting in and around Holtsee, Lieutenant Colonel Wardenburg and 2 battalions of the Russian-Prussian legion and the enemy train marched from Sehested to link up with Dörnsbergs vanguard in Gross Wittensee. Lieutenant Colonel Wardenburg were confident that no Danish forces were in the immediate vicinity of his column so he had neglected to deploy any vanguard, rearguard or flankers. Lieutenant Colonel von der Goltz moved his 1st Regiment of Russian-Prussian hussars into Sehested shortly after Wardenburgs departure. Here von der Goltz deployed the 3rd Squadron towards Holtsee as a reconnaissance force. Under cover of darkness the advanced guard of the 3rd squadron rode directly into the Danish forces near Holtsee. The Danes quickly disarmed the hussars, and the interrogation of the hussars gave the Danes a clear impression of the hostile movements going on near Sehested.
Upon hearing the reports of enemy activity, L´Allemand´s brigade deployed for battle. The Polish Uhlans rode through Holtsee followed by the Holstenske Sharpshooters 1st battalion. This small force made its way towards Haby to cut off the enemy rear guard that had been observed when it marched west (around Holtsee).
The Uhlans quickly reached Wardenburg's train, which they overran taking only few casualties. The entire train were captured, as were the 70 man assigned to guard it. The prisoners and captured wagons were hurried back to the Danish lines around Holtsee.
Meanwhile the Prince of Hessen had reached Holtsee along with the Danish main force. He quickly realized that the roads to Rendsburg and Slesvig were held by hostile forces. He decided to force a gab in the enemy lines near Sehested and thereby open the road to Rendsburg. This move called for a complete victory over Walmoden's corps, as it was of prime importance to keep Walmodens force at a safe distance while the Danes marched towards Rendsburg after the battle. Meanwhile it was very important to keep Dörnbergs brigade away from the fighting so that it couldn't reinforce Walmoden once the Danes attacked.
The Danish 1st Brigade were the least fatigued, so they were assigned with the job of keeping Dörnbergs brigade away from the main engagement. The 1stBrigades chief-of-staff Captain Rømeling was dispatched to Haby with a small force consisting of 3 battalions (the Queens 1st, Holsten 3rd and 4th) along with a jaeger company from the Queens 2nd and a
squadron of hussars. This force moved forward covered by skirmishers and it quickly reached and secured the hamlet Haby. Wardenburgs forces were just outside of Haby, where they remained in cover of the forest. From their cover behind the trees in the small forest the enemy fought a delaying action against Captain Rømelings force. Dörnberg reinforced his left flank north of Haby with the Kielmanseggske jaegers and marched with his remaining troops towards Eckernførde to block the Danish line of retreat north. It didn’t occur to Dörnberg that the Danes had no plans of going to Eckernførde, until he himself reached Marienthal and received a report form a squadron of hussars there. By then Dörnberg had wasted precious time marching.
Meanwhile the Danish vanguard (3 chasseur companies from the 1st brigade supported by l´Allemand's brigade) had moved down the road towards Sehested. It was suddenly stopped by enemy forces occupying the high ground east of the Sehested Manor. Skirmishing evolved as the Danes tried to clear the road. A brief pause soon occurred in the skirmishing as both forces brought up reinforcements. Behind the Danish vanguard came Oldenborgske Infantry regiment on the road in columns. The Fyn 1st and Slesvig 1st deployed to the right of the Oldenborgske regiment. Behind these came Fyn 2nd in column (also on the road). As reserve were 6 squadrons of cavalry (2 hussar, 2 Fynske Regiment Light Dragoons and 2 Holstenske cavalry regiment) deployed on the field behind Fyn 1st and Slesvig 1st. The army train had at this time reached Holtsee and were preparing to move on.
While the Danes deployed for battle Walmoden moved battalion Anhalt, 6th and 7th Russian-Prussian battalions and 2 cannon (battery Wiering) to Sehested. He ordered lieutenant colonel von der Goltz to defend the town by all means. Walmoden then send an adjutant to Dörnberg explaining the current events, and he ordered Ahrentsschildts Russian-Prussian legion to move to his assistance with all possible haste. The remainder of Walmodens forces also received orders to march to the battlefield as fast as possible.
The Prince of Hessen ordered a general advance on Sehested at 9 o'clock. The light battalions of l´Allemands brigade (sharpshooters and the Slesvigske jaegers) spread out as skirmishers along with the jaeger companies from the 1st brigade. The Danish skirmishers advanced quickly upon the enemy 6th battalion skirmishers, who started to fire at the advancing Danes. The enemy 7th battalion (deployed on the left side of the Ejder river) supported the 6th battalion by firing at the advancing skirmishers. General Schulenburg send a couple of companies of the Oldenborgske 4th out on his left flank to support the troops there. Behind the light battalions skirmishing came 3rd Jydske Infantry regiment 1st battalion formed in line, marching with their muskets shouldered as if on parade.
The enemy battalions were, after fierce resistance, thrown back to the northern part of Sehested, where the enemy took cover and prepared a stiff defense of the town supported by battery Wiering. But the Danish assault columns were at this point unstoppable. The Oldenburgske 1st charged the enemy positions with their grenadier company leading the battalion. Despite murderous defensive fire, they proceeded to overrun the enemy positions. The victorious Danes pushed the enemy back through the entire town in one long fierce attack. The 6th Russian-Prussian battalion suffered severe casualties, a lot of them were taken prisoner.
Sehested were entirely in Danish hands at 10:30, and the 2nd Danish brigade still in reserve. The push towards Holtsee and the capture of Sehested by the Danes had taken Walmoden completely by surprise. He had dispersed his army corps in such a way that he was incapable of launching any immediate counterattacks. But he now knew that he had the entire Danish force opposing him, so he decided to stall them until his troops commanded by Dörnberg could attack the Danes in the rear. At 11.00 o'clock Walmoden had gathered a force of 11 battalions, 10 squadrons and 18 pieces of cannon. He immediately advanced the Russian-Prussian brigade (1st, 2nd and 5th battalions) over the bridge at Osterrade. The two leading battalions of the brigade turned left, to march across the fields south of Sehested to reach the Rendsburg road, but they became engaged with Danish forces and was soon cut off from the main force. The last battalion (the 5th) moved down the road to retake Sehested, while battery Wiering supported the attack from a position left of the road. The 3 Danish companies of Oldenborg 1stwhich defended the southern part of the town poured musket fire into the advancing 5th battalion, but had to withdraw to a nearby ditch as they quickly became outnumbered. The 5th battalion also captured a Danish howitzer that had been deployed to support the companies in the southern part of Sehested.
Soon after the enemy 5th battalion success, General Schulenberg led the Fynske Regiment Light Dragoons in a charge to stop the 5th battalion. When hit by screaming and shouting charging cavalry the 5th battalion panicked. The two leading companies of the 5th fled to the sides of the road but the companies in the rear of the battalion, which still hadn't seen the Danish cavalry were overrun before they could fire a single shot. The 5th battalion quickly disintegrated as the remains of the battalion tried to flee back to Osterrade. The 2 cannons of battery Wiering was also captured during the cavalry charge. The enemy 6th battalion and battalion Anhalt, which were reforming south of Sehested, were quickly routed as the dragoons continued their charge. Several prisoners were taken by the Danes before the dragoons were overwhelmed with fatigue and had to return to the friendly lines, they had been less than 150 men when the charge started.
Of the Danish infantry that had advanced in support of the cavalry, the Oldenborgske infantry regiment took a huge number of prisoners. The Slesvig 1st and Fyn 1st reached the southern edge of Sehested while the 3rd Jydske infantry regiment 1st were ordered to cover the cannons deployed to the left of the regiments line. Only the 3 cannon of battery Friis remained west of the town along with 2 companies of Fyn 2nd. The attack of the dragoons had a devastating effect. The enemy lost 2 cannons and hundreds of troops were taken prisoner, and even worse, the enemy had suffered a severe blow to morale. Walmoden decided in spite of this to attack again. At noon he ordered 1st Hussar regiment commanded by von der Goltz to advance towards Sehested. On its way the regiment captured a few Danish dragoons who had lost their horses in the charge, before the hussars came under artillery fire and had to withdraw in disorder losing several casualties. The remainder of the 5th and 6th battalions and battalion Anhalt had meanwhile retreated to safety on the other side of the canal.
Battalion Lauenburg and Captain Holtzermans 5 companies followed by the Mecklenburg jaegers and the demoralized 7th battalion had advanced during the failed hussar attack. The Danish artillery left and south of Sehested directed a murderous fire upon the advancing enemies. The attack soon ground to a halt in the face of the Danish artillery. Battalion Lauenberg deployed as skirmishers and began engaging the Danish musketeers and grenadiers in southern Sehested. A fierce skirmish soon evolved. The Prince of Hessen ordered the Danish hussars (2nd squadron) commanded by Major Späth and a couple of squadrons of Fynske Regiment Light Dragoons to charge the advancing enemy battalions. The hussars cut through battalion Lauenburgs skirmish line without pausing to take prisoners and charged the 7th battalion, which dissolved when faced with a cavalry attack. The men of the 7th battalion fled, many dropping their muskets, hordes of them surrendered to the Danish hussars. The few remaining troops of the 7th battalion fled towards the Osterrade bridge where the cavalry charge evolved into a melee with fleeing enemy soldiers trying to cross the bridge. Meanwhile the Danish dragoons had attacked battalion Lauenburg and the Holtzerman skirmishers who were overrun and cut down. Only the Mecklenburg jaegers avoided disaster by forming small squares on a field and maintaining a steady fire to keep the Danish cavalry at bay.Walmoden were forced to order the Mecklenburg mounted jaegers forward from Klüvensik to cover his retreating battalions. The gallant mounted jaegers, commanded by Prince Gustav of Mecklenburg leading the 2nd squadron attacked along the Sehested road, where they drove the Danish hussars and dragoons backwards. The charge cut through Oldenborgs skirmish line and on towards the southern part of the town, where the mounted jaegers charged at the Danish artillery. Before they reached the cannons the mounted jaegers became covered in powder-smoke from muskets as the Fynske and Slesvigske musketeers (lying in cover behind hedges on both sides of the Sehested road) send bullets shredding into the squadrons flanks. In front of the leading squadron the Danish artillery started pouring shrapnel at the horsemen. The cavalry attack stopped dead in its track as the leading squadron of 120 men were reduced to only 6 men in a matter of minutes. Prince Gustav fell wounded and was captured by the Danes (the squadron later had to be rebuilt from scratch back in Mecklenburg). The costly charge of the mounted jaegers had not been a total disaster as several prisoners taken by the Danish cavalry were freed during the mounted jaegers attack on the Danish horsemen. The remains of the 7th battalion along with battalion Lauenberg withdrew to safety during the attack and began to reform (both of the battalions were so demoralised and fatigued that they were useless for the remainder of the battle).
Now Walmoden realised that Sehested couldn't be taken by a frontal assault, and he therefore ordered his artillery to take defensive positions along the Ejder river. Shortly thereafter he ordered the 2 Russian-Prussian battalions (1st and 2nd), which were currently positioned west of the road, to attack Sehested from the south-west. The two battalions had since 11 o'clock been advancing on the Rendsborg road, but they had been forced to form thin skirmish lines as Danish artillery had shelled them remorselessly (neither of the battalions were well trained in the use of the skirmish formation and they therefore advanced painfully slow). But when the Danes turned their full attention to the ongoing battle south of Sehested the two battalions managed to form columns (around 13:00) and advance in a steady pace over the fields, where they encountered the two companies from Fyn 2nd battalion that had been detached to cover the 3 guns of Friis battery also west of the town. The two companies offered stiff resistance and after a fierce fire fight the Danish companies were running desperately low on ammunition. The situation for the Danes suddenly became critical when the two enemy battalions started pushing the companies back. The Prince of Hessen had expended his last reserves in the fight south of town and were now considering to disengage the enemy before his right flank would be turned.
The situation changed rapidly when 3 Danish battalions, led by captain Rømeling appeared in the northern part of Sehested, marching towards the battle. Rømeling had earlier been detached to stall Dörnberg's troops north of Holtsee. Rømeling had noticed that the force opposing him north-west of Holtsee were nothing more than a couple of enemy companies (and not an entire brigade as the Prince of Hessen had feared). The enemy companies hadn't engaged in any hostile action all day and seemed very reluctant to fight the Danes. Rømling had then decided that his force were more needed elsewhere and marched his main force towards Sehested, leaving 1 jaeger company and the 6th Squadron of hussars to cover his rear. Rømling led his 3 battalions (The Queens 1st, Holstenske 3rd and 4th) of which one deployed in a thin skirmish line and the other 2 in column, forward against the two advancing enemy battalions west of Sehested. The 1st and 2nd Russian-Prussian battalions had to retreat after 15 minutes of intense fighting. They were pursued by Queens 1st and Holstenske 4th, who made several bayonet charges into the rear of the retreating enemy, taking hordes of prisoners and leaving several dead enemies on the fields south-west of Sehested. Holstenske 3rd followed behind as reserve.
General Schulenberg saw the two enemy battalions break and rout and quickly responded by leading his Danish brigade south from Sehested, supporting captain Rømling's flank. Schulenberg forced his way through the remaining opposing enemy forces and almost reached the commanding enemy general in Osterrade. The entire Danish train moved unhindered through Sehested while the last attack was taking place and continued along the road to Rendsborg. The Prince of Hessen had completed all his objectives when the battle ceased at 15:00. He had destroyed Walmoden's main force and the ground north of the Ejder river were controlled by the Danes.
Later that night the 1st and 2nd brigade of the Danish corps arrived in Rendsborg, singing victoriously despite of their fatigue. Along with them were a huge number of prisoners and 2 captured cannons (now at display in Copenhagen in the military museum "Tøjhusmuseet").
L´Allemand were left in Sehested with his 2 light battalions. During the evening he skirmished with the Mecklenburg jaegers who had occupied Osterrade. During the night he withdrew to link up with Holstenske Sharpshooters 1st, Battery Gerstenberg and the Polish Uhlans near Mühlenberg. Slesvig 2nd battalion were nearby as a rear guard reserve. The entire rearguard led by l´Allemand arrived in Rendsborg at 5 o'clock the next morning.
The Danish casualties were (estimated as sources vary) 550 men. Broken up like this: 17 wounded officers, 66 dead (all ranks), 319 wounded and 146 missing. Walmoden lost more than 2.000 men. 22 killed and wounded officers, 522 dead soldiers, 22 officers captured and 632 of all other ranks captured. About 1.000 men were missing.
Avant-garde : François Antoine Lallemand
2e bataillon de chasseurs de Schleswig
1er et 2e bataillons de fusiliers de Holstein
1er bataillon du 3e régiment de Jutland
4 escadrons du régiment de cavalerie lourde de Holstein
2 escadrons du 17e régiment de lanciers polonais (lituaniens)
batterie von Gerstenberg (8 pièces de 6) auraient-ils perdu leurs 2 autres pièces ?
Corps principal : Frédéric de Hesse
1re brigade : Graf SchulenBurg
1er et 4e bataillons du régiment de Oldenbourg ainsi que 3 compagnies du 2e bataillon
3e et 4e bataillons du régiment de Holstein
2e et 6e escadrons du régiment de hussards danois
Batterie von Gonner (8 pièces de 3) auraient-ils perdu leurs 2 autres pièces ?
Batterie Koye (8 pièces de 6) auraient-ils perdu leurs 2 autres pièces ?
2e brigade : Von Abercron
1er et 2e bataillons du régiment de Funen