Complex sentence: Their task was to insert 25 km across the border and establish OPs overlooking the Northern end of the Kacanik defile, a key choke point on the Main Supply Route which the main body of the NATO force would follow into Kosovo.
Split into simpler sentences: Their task was to insert 25km across the border and establish OPs overlooking the Northern end of the Kacanik defile. This was a key choke point on the Main Supply Route which the main body of the NATO force would follow into Kosovo.