Line of defense and Roadblock

Line of defense noun - Any organization whose responsibility it is to defend against something.

Roadblock and line of defense are semantically related. In some cases you can use "Roadblock" instead a noun phrase "Line of defense".

Roadblock noun - Any condition that makes it difficult to make progress or to achieve an objective.

Line of defense and roadblock are semantically related. You can use "Line of defense" instead a noun "Roadblock".