Complex sentence: The first encounter took place on 13 May 1941, just 8 days after leaving port, when "U- 111" came across the British merchant vessel "Somersby" and sank her just south of Iceland.
Split into simpler sentences: The first encounter took place on 13 May 1941, just 8 days after leaving port. On that day "U- 111" came across the British merchant vessel "Somersby" and sank her just south of Iceland.