Complex sentence: On the way, they are unsuccessfully pursued by armoured cars and fighter planes, being led to an officer named Mull Pasha, who is in reality Tintin's old antagonist, Dr. Müller.
Split into simpler sentences: On the way, they are unsuccessfully pursued by armoured cars and fighter planes. The forces are being led to an officer named Mull Pasha, who is in reality Tintin's old antagonist, Dr. Müller.