HOI4 Sea Lion Guide 2026

If you want to invade the UK in Hearts of Iron IV, several routes are available depending on your strength and tools. A powerful navy opens the southern coast, overwhelming air lets you land paratroopers in safer northern ports, and pre-war or supply-based tricks can help weaker nations. This guide covers the clean, honest naval route, airborne drops, timing-based launches, and supply handling—plus templates and designs for each approach.

Quick answer

Pick the landing method first

The way you invade the UK depends on your navy, air force, and overall country strength. The most straightforward options are:

• Landing on the southern coast using a strong navy, with air support if available.
• Air-superiority-based naval invasion—bombers and fighters keep the sea clear even with a poor fleet.
• Paratrooper drops, if you can secure a port and bring in reinforcements.

Majors like Germany, Italy, or Japan have the industry for powerful fleets and overwhelming air, but even weaker minors can use timing tricks: build up dominance before war starts, or snipe a harbor with a well-timed invasion from a smaller sea zone. The ideal method matches your tools: navy for the south coast, air for drops, or cheese for minors without either.

Land on the southern coast when your navy is strong

The classic, honest approach is a naval invasion from northern France targeting Portsmouth and Dover—the UK’s main southern ports.

This coastline is heavily defended: Portsmouth and Dover have strong static anti-air, and Dover often has coastal forts. Even so, landing here is faster, supply routes are easier to manage, and you only have one front to watch. You can encircle fortified Dover by adjusting which province you launch from; clicking adjacent landing tiles gives partial control over invasion spread and assignments.

After landing, the southern supply lines keep your divisions fighting, and the narrow front reduces management overhead. This route lets you cut off parts of the coast and isolate enemy divisions early for easier cleanup.

Run your fleet and planes for a clean naval invasion

To ensure your invasion launches and lands safely, organize your fleet and air missions for both coverage and dominance.

1. Set destroyers to patrol, larger ships to strike force, submarines for convoy raiding. 4:16
2. Assign air superiority and naval strike missions over the Channel. 4:45
3. Switch the fleet to naval invasion support and shore bombardment after the invasion fires. 5:14
4. Send strong divisions quickly—speed matters more than sheer numbers. 5:41

Keep your main ships and air missions focused where the invasion will cross. Once divisions hit the coast, push aggressively to prevent supply issues and enemy reinforcement buildup.

Keep supply under control after you land

Without solid supply, any bridgehead will collapse fast. Manage logistics carefully:

1. Land only a few strong divisions—avoid oversaturating your port with weak units. 6:09
2. Prioritize quality over quantity—strong divisions handle attrition and resistance better. 6:38
3. Block sea regions in the supply map to change convoy routes and force supply through safer paths. 7:07
4. Watch for fuel shortages—it's a sign of serious supply problems. 7:37

Divisions stranded without supply lose organization and combat power. If routes default through puppets or unwanted paths, use sea-zone blocks to force supply from France or allied ports. Logistics companies, floating harbors, air supply, and safe convoy routes become critical if your infrastructure is weak.

Use air superiority to beat a weak navy

If your navy cannot contest the Royal Navy, air power can make up the difference. Assign bombers and fighters to the Channel or target sea zones; the enemy fleet is much less likely to enter areas dominated by your air force. This tactic works especially well for Germany, with minimal investment in naval production needed.

Naval bombers (including converted CAS with bomb modules) force the Royal Navy to retreat, letting weak fleets patrol on "do not engage" or raid convoys. Submarines distract the enemy and hit their logistics.

This method can reach over 50% sea dominance in a single day, rising to 68% the next. Once the invasion fires, assign your planes directly to the ground offensive for maximum support. The key is timing; trigger the landing as soon as dominance is achieved before enemy fleets regroup.

Drop paratroopers onto a safe harbor

Paratrooper drops bypass the naval fight but require strict preparation.

1. Secure over 70% air superiority in the target region before issuing the drop order. 11:29
2. Allow 7 days for the paratroop mission to prepare—a short setup compared to naval invasions. 11:29
3. Use a starting airfield (within range) and provide enough transport planes for each airborne division. 11:57
4. Avoid southern England—static anti-air makes Portsmouth/Dover virtually impossible for airborne landings. 11:57
5. Target Hull-Newcastle region instead for safer drops and supply lines. 11:57

After landing, prioritize capturing a harbor so reinforcements and supply can arrive. Paratroopers do not hold well in prolonged combat—send in strong follow-up divisions as soon as a port is secured.

Set up cheesy pre-war dominance and North Sea tricks

If your navy and air are both weak, exploit pre-war setup or minimal sea requirements.

1. Plan the naval invasion before declaring war—if the invasion is ready, it triggers as soon as you join the conflict. 14:03
2. Launch the war once dominance is established—the invasion fires instantly, giving the defender no time to counter. 14:47
3. Target the East Midlands (or specific northern harbors)—the route can require dominance in the North Sea only, not the Channel. 17:12
4. Pair subs on convoy raiding and set the fleet to do not engage in sea zones (minimizes combat risk). 17:12

These tricks let weak nations snatch a foothold without directly confronting the Royal Navy. Splitting your submarines and fleets into multiple small groups can also maximize distraction.

Handle bad RNG and disengage bad fights

Even with optimal setup, naval combat has randomness—the Royal Navy may strike harder or ignore your distractions. Submarines, even in groups of one, can draw enemy focus, but since recent patches, detection increases mean they are wiped out more quickly.

If your fleet is engaged, use the disengage button in the naval battle window. Spam it repeatedly. This often lets ships escape before heavy losses build up.

You may need to disengage through several battles, losing some ships each time. If the enemy keeps pressing, reload and try again—sometimes waiting a few weeks before another attempt shifts the enemy fleet away from your route. Save before launching the invasion, even in ironman, to retry if the initial approach fails.

Use the right templates and cheap ships for each country

Matching your invasion plan to the right division and navy composition is essential for execution. The following table summarizes useful templates and approaches for different nations and invasion methods.

Adjust division width, support companies, and special forces composition to the job: marines for coastal landings, tanks for fast pushes, mountaineers for rough terrain. Cheap ships help with sea dominance when a real fleet is out of reach—especially for minors.

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