Complex sentence: During the German-led Axis invasion of Yugoslavia in April 1941, she served with the 1st Monitor Division and along with her fellow monitor, she laid mines in the Danube near the Romanian border during the first few days of the invasion.
Split into simpler sentences: During the German-led Axis invasion of Yugoslavia in April 1941, she served with the 1st Monitor Division. Along with her fellow monitor, she laid mines in the Danube near the Romanian border during the first few days of the invasion.