Complex sentence: The Japanese national football team is very successful at a international level, and has competed in the 1998,2002,2006, and 2010 FIFA World Cups, and their best result was Round 2 in 2002 and 2010.
Split into simpler sentences: The Japanese national football team is very successful at a international level, and has competed in the 1998,2002,2006, and 2010 FIFA World Cups. Their best result was Round 2 in 2002 and 2010.