Fortifications of Sweden

Early Fortifications of Sweden were built to defend self-governing provinces, with rapid expansion of forts in the 14th Century and again in later in the 16th Century when Sweden became independent, needing to protect its borders. 
Changes in the position of borders led to fortifications changing owner, to and from Sweden, some became redundant and a few forts were given major upgrades for improved technology over the centuries.
List of Fortifications.
12C
13C
14C
Hundred Years' War and Black Death
15C
Unification under one king and expansion of territory with first Union with Norway and Denmark
16C
Sweden gains independence and Protestant Reformation, Livonian War, creation of Sweden's first professional army.
17C
Ingrian War, Kalmar War, Thirty Years' War and Second Northern War saw Swedish territory expand.
18C
After Swedish defeats in the Great Northern War as well as in the Russo-Swedish War of 1741-1743, there was a need to construct fortifications to guard both the border as well as the coast of Finland.
19C
Union with Norway after Norway ceded to Sweden by Denmark
20C
Dissolution of the union between Norway and Sweden, neutral in First and Second World Wars. Cold War era.
[‡] Currently in use by the Swedish Military