Question: What increased pressure forced the Romans to abandon their line of defense concept at the end of the 4th century?
Sentence: The Empire built another line of defense at the north border (the so-called Donau-Iller-Rhine-Limes), but at the end of the fourth century the increased Germanic pressure forced the Romans to abandon the linear defence concept, and the Swiss plateau was finally open to the settlement of German tribes.
Answer in sentence: yes