Complex sentence: Brazil had no practical access to its own territory of Matto Grosso except by sailing from the Atlantic Ocean up the River Paraguay (see map); fear that Paraguay might interfere with the navigation was a source of conflict.
Split into simpler sentences: Brazil had no practical access to its own territory of Matto Grosso except by sailing from the Atlantic Ocean up the River Paraguay (see map). Fear that Paraguay might interfere with the navigation was a source of conflict.