Historically coastal defense has been a task for the Coastal Fleet. The task is sought solved in a number of ways.
Prominent among these are coast-defense armourclads, of which ten remain in service, with probably three of these destined to be removed from service under the treaty (
data on the Nordmark coast-defense armourclads). These armourclads are of a typical Scandinavian type, being essentially scaled-down pre-dreads. These are supported by smallish coastal armoured cruisers (armed with 5.9inch guns), as well, as some scout cruisers, backed up with destroyers and torpedoboats.
These armourclads are complimented by coastal artillery forts protecting a number of significant sites. Coastal artillery uses guns of a number of sizes, from small 1.85inch QF-guns to (so far) 11.1inch rifles and howitsers. Recent emplacements have been seen to favour enclosed turrets for heavy guns, with those for regular rifles being identical to those carried by ships. Medium and heavy guns installed since 1900 include the following calibres: 4.3inc/11cm; 5.9inch/11cm; 8.2inch/21cm; 9.4inch/24cm; and 11.1inch/28cm, reflecting the calibres of guns used on ships in the Coastal Fleet.
It was until recently the intention to phase out the 8.2inch guns in favour of 9.4inch guns and howitsers, but with the recent naval treaty, the days of the 9.4inch guns seem doomed, while 8.2inch guns will be developed further; this is in order to increase navy-wide weapons commonality. Turrets tend to be single-gun turrets, withr elatively high elevation; a good number of the 8.2inch, 9.4inch, and 11.1inch mounts are howisers, and very often they are placed so that they fire indirectly (with any return-fire by necessity being indirect as well, greatly favouring the forts). The forts also enjoy a number of minelayers, and generally tend to have at least one torpedo-battery; recently constructed batteries will us 21inch/53.3cm torpedoes.
There are no railway-guns, as this is not considered to be of much use for coastal defense.
The navy in general has so far not had an integral naval infantry, arming sailors if and when necessary. The Coastal Fleet, however, has since its inception included in its organisation units of infantry carried on the vessels. The tasks of the Coastal Fleet include defense against naval invasion near the coast, and support of army-units. It thus makes sense to carry these units of infantry, both to provide immediate infantry-defense against invasion, and to provide immediate support for the army-units it supports.
Such units are also provided to the fortresses (forts are organised in fortresses, each of which has a tasked area - the defence of Oslofjord is divided in Outer Oslofjord Fortress, and Oscarsborg Fortress, for instance) - in wartime at minimum a battalion to each fortress, though in peacetime a cadre of no more than one company (often less - Outer Oslofjord and Oscarsborg fortresses between them have the equivalent of one company and one platoon total as their peacetime cadre, for instance)is maintained to each fortress.
The role of the units assigned to the fortresses is clear enough - the prevent the fortresses from being captured by land-attack. It is common that coastal forts are surrounded by strongpoints to their land-side - bunkers, blockhouses, and similar. Battalions tend to be equipped with mountain-howitsers (which can be packed in loads small enough to be manportable) and mortars, as well as machine-guns.
Plans are unfolding to enlarge the Coastal Fleet infantry-organisation, and apply it to the entire navy, including the battle-line. It is thought possible to embark an entire company of naval infantry; in addition more battalions will be created, to be used in situations where this is required. These will remain light infantry, not entirely dissimilar to the British model.
The naval infantry is termed
Kystjeger (rough translation being
Coastal Ranger); they use navy commissioned ranks and parade-uniforms, but the battle-uniforms introduced 1915 are more like those of the army; distinctions retain a naval flair, nonetheless, and non-commissioned ranks are still entirely naval.