How coastal battleships deter a close blockade

How can coastal battleships defend a country against naval coercion?

They force a stronger fleet to risk expensive ships near the coast without creating an equivalent threat to its own home waters.

A country with limited dependence on distant maritime trade can concentrate its fleet on preventing coercion close to home. Coastal battleships make a close blockade dangerous because the attacker must commit powerful ships to overcome them. Their short reach also limits the threat they pose abroad. Germany's ocean-going battle fleet provides the comparison: it challenged British naval security directly, whereas a coastal force could complicate intervention without threatening Britain itself.