A Strategic Reassessment: Denmark on the Eve of War

By the mid-19th century, the Kingdom of Denmark stood at a crossroads. The Napoleonic Wars had stripped it of Norway and its navy, and the Congress of Vienna had reduced its once formidable Baltic influence. Yet Denmark retained control of the Duchies of Schleswig, Holstein, and Lauenburg – a patchwork of German-speaking and Danish-speaking territories that formed a crucial land bridge to the German Confederation. The population of these duchies was deeply divided: the German-speaking elites in Holstein and southern Schleswig sought closer ties with Prussia, while Danish nationalists in northern Schleswig wanted full integration into the Danish state. This tension erupted in March 1848, when a rebellion in the duchies, supported by Prussian troops, sparked the First Schleswig War (1848–1851).

For Denmark, the stakes could not have been higher. Losing the duchies would not only sever the kingdom’s landmass from its southern provinces but also cede control of the Kiel Canal and key Baltic approaches. The Danish Navy, though only a tenth the size of the British or French fleets, was the only force that could project power beyond the coastline and threaten enemy supply lines across the Baltic. The narrow Nares straits – a strategic choke point near the island of Fehmarn – became the focal point for a decisive naval showdown.

The Danish high command understood that the Prussian-led coalition planned to force a passage through Nares to reach the open Baltic, where they could blockade Copenhagen and land troops on Zealand. If the straits fell, the war would be lost. Vice Admiral Christian Wulff, a seasoned tactician who had fought in the Napoleonic Wars and led the bombardment of Hamburg in 1848, was ordered to concentrate his squadron and prevent any enemy breakthrough.

The Buildup to Battle: Squadrons and Strategies

Throughout the spring and summer of 1849, both navies prepared for the confrontation. Wulff assembled a heterogeneous force of ten warships, including two steam frigates (Hekla and Gejser), three sailing corvettes (Valkyrien, Rota, Najaden), and a flotilla of eight gunboats. The gunboats were particularly suited to Baltic conditions – their shallow draft allowed them to operate in the treacherous shallows around Nares, while their heavy carronades delivered devastating short-range fire. The Danish crew had trained extensively in gunnery and maneuvering, but their ships were aging: the sailing corvettes dated from the 1820s, and the steam engines on the frigates were prone to breakdowns.

The opposing coalition fleet, under Prussian Rear Admiral Karl von Briesen, was more modern on paper. It included the steam corvette Preußen, the Austrian paddle steamer Freya, and the sailing frigates Gefion (a captured Danish vessel!) and Venus. Von Briesen’s squadron also carried a significant number of troops for potential landings. His plan was typical of the era: form a line of battle and pound the Danish defenders into submission with broadsides, then exploit the breakthrough with landing parties. What von Briesen did not fully account for was the Danish commander’s willingness to break convention.

Wulff had studied the emerging tactics of steam warfare. He knew that his steam frigates, despite their fragile engines, could operate independently of the wind. Instead of forming a static defensive line across the straits, he positioned his sailing corvettes as bait near the channel entrance, while hiding his steam vessels and gunboats behind the island of Lolland. When the enemy made its move, Wulff intended to strike from unexpected angles, using speed and surprise to disrupt the enemy formation.

The Battle Unfolds: August 17, 1849

At dawn on August 17, lookouts on the Danish corvette Valkyrien sighted the Prussian-Austrian fleet sailing northward in a loose line. Von Briesen had reconnoitered the straits earlier and expected to face only the Danish sailing ships; he believed the steam frigates were still undergoing repairs in Copenhagen. That intelligence gap would prove costly.

The opening phase of the battle was a formal exchange of long-range broadsides as the enemy fleet entered the straits. The Danish sailing corvettes held their fire until the last moment, inflicting some damage on the leading Prussian ships. But the real shock came when Wulff gave the signal: the steam frigates Hekla and Gejser emerged from behind Lolland at full speed, crossing the enemy line and raking several ships with concentrated fire. The Hekla, commanded by Captain Niels Rye, engaged the Prussian flagship Preußen at close range, its shells punching through the enemy’s hull and disabling part of its battery.

The battle descended into a chaotic melee. The Danish gunboats darted among the shallow waters, forcing the larger enemy ships to either run aground or remain in deep channels where they could be targeted. The Austrian paddle steamer Freya attempted to pursue the Gejser but lost a paddle wheel to a lucky shot and had to be towed out of action. For six hours, the two sides exchanged fire at ranges varying from 50 to 500 yards, with neither able to achieve a clear advantage.

A turning point came when a shell from the Prussian Gefion struck the Hekla’s engine room, severing a steam pipe and causing scalding steam to fill the compartment. Danish engineers, working under fire, managed to isolate the damaged section and maintain steam pressure to the remaining engine. The frigate continued to fight, albeit at reduced speed. This incident, later studied by naval engineers, highlighted the need for better protection of propulsion systems – a lesson that would influence future designs.

As the sun set, both admirals faced a decision. Wulff had prevented the enemy from breaking through the straits, but his squadron was damaged, and his crews were exhausted. Von Briesen had lost a gunboat sunk, the Freya crippled, and over 60 casualties; the Danes suffered 50 casualties and the loss of one gunboat. Neither side could claim decisive tactical victory. Yet the strategic advantage clearly belonged to Denmark: the straits remained in Danish hands, and the enemy’s landing force never set foot on Zealand.

Casualties and Losses: A Detailed Breakdown

The Royal Danish Navy lost the gunboat Støren (struck by a Prussian shell that ignited its powder magazine) and suffered damage to two ships. Among the casualties were 12 killed and 38 wounded, including two officers. The coalition forces lost one ship sunk, the paddle steamer Freya heavily damaged, and the Preußen required weeks of repairs. Coalition casualties were 18 killed and 44 wounded. The disparity in damage reflected the effectiveness of Danish gunnery, which caused more structural destruction, while enemy fire tended to be less accurate due to the moving targets presented by the agile Danish steam vessels.

Aftermath: Political and Military Fallout

The news of the battle reached Copenhagen on August 21. The city erupted in celebration, with crowds cheering the navy and especially the steam frigates. The government immediately capitalised on the success: King Frederick VII awarded Wulff the Grand Cross of the Order of the Dannebrog, and the Admiralty published a detailed account of the battle that was circulated across Europe. The battle boosted national morale at a critical moment – just weeks earlier, the army had suffered defeats at Kolding and Fredericia.

Prussian and Austrian commanders were forced to abandon their plan for a direct attack on Copenhagen via the Baltic. Instead, they turned to a distant blockade – a less effective strategy that allowed Danish merchant ships to continue operating from Swedish and Norwegian ports. The blockade also strained Prussian resources, as maintaining a constant naval presence required substantial coal and supplies. The war dragged on for another year, but the Battle of Nares had effectively neutralised the enemy’s naval threat.

Diplomatically, the battle influenced the peace negotiations that culminated in the Treaty of Berlin (1850). The treaty temporarily preserved Danish control over Schleswig and Holstein, though the underlying tensions remained unresolved – tensions that would erupt again in the Second Schleswig War of 1864. Nevertheless, in 1850, the outcome of Nares gave Denmark a stronger hand at the negotiating table.

Transformation of Danish Naval Doctrine

The Battle of Nares triggered a profound re-evaluation of Danish naval strategy. Before 1849, the navy was largely viewed as a coastal defence force, reliant on older sailing ships and fixed fortifications. Wulff’s successful use of steam frigates as independent strike assets convinced the Admiralty that Denmark needed a modern, steam-powered fleet capable of offensive operations in the Baltic.

The 1851 Naval Act, passed by the Danish parliament, allocated substantial funds for new construction. Over the next decade, Denmark launched four steam corvettes (Absalon, Helge, Esbern Snare, and Thyra), two paddle steamers, and converted several old sailing ships to auxiliary steam power. The new ships incorporated lessons from Nares: armoured engine rooms, watertight compartments, and improved bilge pumps. The Danes also began experimenting with early torpedoes – small explosive boats that could be launched from fast steam launches – anticipating the “jeune école” tactics that would become popular in the 1870s.

Naval training underwent a similar transformation. The Naval Academy added courses in steam engineering, thermodynamics, and electrical signalling. Officers were required to spend time on steam vessels to gain practical experience. The tactical doctrine shifted from the classical line of battle to a more flexible approach: small squadrons operating independently, using terrain and weather to their advantage, and exploiting steam mobility to concentrate force rapidly.

Technological Legacy: Steam and the Baltic Environment

The Battle of Nares also highlighted the unique demands of Baltic naval warfare. The Baltic Sea is shallow, with average depths of only 50 metres, and its waters are brackish – less dense than ocean saltwater, which affects propeller efficiency. The straits around Denmark are laced with sandbanks, reefs, and shifting channels. Conventional sailing navies operated at a disadvantage here, as they required deep, clear waters to manoeuvre. Steam power allowed Danish ships to operate in these confined spaces, using currents and tide to their advantage.

Furthermore, the battle demonstrated the importance of logistical support. The Danish gunboats were able to sustain combat longer because they could be rapidly resupplied from coastal depots on Lolland and Falster. In contrast, the Prussian-Austrian fleet had to bring all coal and ammunition from bases in Kiel and Wismar, limiting their endurance. This lesson impressed on Danish planners the need for a network of supply stations along the Baltic coast – a system that would remain important through the 20th century.

Commemoration and National Identity

The Battle of Nares occupies a special place in Danish historical memory. On the centenary of the battle in 1949, the Danish Parliament issued a commemorative coin featuring a steam frigate and the profile of Vice Admiral Wulff. The Danish Naval Museum in Horten houses a permanent exhibition on the battle, including the bell of the Hekla and the battle flag flown from the Gejser. Reconstructions of the gunboat Støren are displayed at the Maritime Museum in Helsingør.

August 17 is observed as Danish Naval Day, with ceremonies at the Aarhus Naval Base and at the memorial stone on the island of Lolland, overlooking the straits. The Danish Maritime Heritage Association stages an annual reenactment, using restored steam launches and ceremonial cannon fire. School textbooks include the battle as a key example of Danish ingenuity and resilience in the face of adversity.

The battle also shaped Danish self-perception as a maritime nation. Even after the loss of the duchies in 1864, the memory of Nares sustained the belief that Denmark could defend its waters against larger powers. This sentiment persisted into the Cold War, when Danish naval forces were tasked with guarding the Baltic Approaches against potential Warsaw Pact incursions – a role that echoed the strategic imperative of 1849.

Critical Reassessment Among Historians

Modern naval historians have debated the extent of the battle’s significance. Some argue that its tactical stalemate makes it an overrated episode: it did not prevent Denmark’s ultimate defeat in the Second Schleswig War, and the navy’s performance was partly due to luck. Others contend that Nares was a watershed moment because it forced the Danish military establishment to modernise, a process that arguably saved the country from total collapse in the 1864 conflict. The British naval historian Andrew Lambert has cited the battle as a classic example of “marginal naval warfare,” where a weaker power uses local knowledge and technological adaptation to achieve strategic parity.

What is undisputed is the battle’s role in preserving Danish control of the Baltic straits during a critical phase of the First Schleswig War. Without Wulff’s squadron, the enemy could have landed troops near Copenhagen, potentially forcing Denmark to surrender in 1849. The battle thus bought time for diplomacy and military reform – time that ultimately allowed Denmark to survive as an independent nation, albeit with reduced territories.

Broader Implications for European Naval Power

The Battle of Nares was followed with keen interest by naval powers across Europe. The French Navy, then under the reformist minister Lord Palmerston, dispatched observers to study the Danish steam tactics. The British Royal Navy, which had long dominated global seas, began experimenting with steam frigate independent operations based on the Danish model. The United States Navy, still recovering from the War of 1812, took note of the importance of shallow-water gunboats – a lesson that would prove valuable in the American Civil War less than fifteen years later.

In many ways, the battle prefigured the naval arms race of the late 19th century, where steam power and technological innovation became the primary determinants of naval strength. The Danes, constrained by limited budgets and geography, were forced to innovate out of necessity. Their success at Nares demonstrated that even a small navy could influence the course of a major war, provided it was properly led and equipped.

Enduring Lessons for Modern Naval Strategy

The Battle of Nares offers timeless lessons for contemporary strategists. It underscores the value of adaptation – taking a new technology (steam propulsion) and employing it in an unconventional way to offset numerical inferiority. It highlights the importance of geography – knowing the local waters and using them to your advantage. And it demonstrates the power of morale – a determined crew fighting for a cause they believe in can hold off a more powerful adversary.

In an era when Sweden and Denmark continue to cooperate on Baltic security through the Nordic Defence Cooperation (NORDEFCO), the strategic lessons of Nares remain relevant. The narrow straits that connect the North Sea to the Baltic are still the key to defending northern Europe. The battle reminds us that dominance at sea is not only about numbers and displacement, but about speed, surprise, and the courage to fight on your own terms.

Further reading: Schleswig-Holstein Wars overview | Danish Naval History Archive | The impact of steam power on naval warfare | Lecture: "Small Navies in Great Power Conflicts"