With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: In 778, he led the Neustrian army across the Western Pyrenees, while the Austrasians, Lombards, and Burgundians passed over the Eastern Pyrenees. The armies met at Saragossa and Charlemagne received the homage of the Muslim rulers, Sulayman al-Arabi and Kasmin ibn Yusuf, but the city did not fall for him. Indeed, Charlemagne faced the toughest battle of his career. The Muslims forced him to retreat. He decided to go home since he trusted the Basques, whom he had subdued by conquering Pamplona. He turned to leave Iberia, but as he was passing through the Pass of Roncesvalles one of the most famous events of his reign occurred. The Basques attacked and destroyed his rearguard and baggage train. The Battle of Roncevaux Pass, though less a battle than a skirmish, left many famous dead, including the seneschal Eggihard, the count of the palace Anselm, and the warden of the Breton March, Roland, inspiring the subsequent creation of the Song of Roland ("La Chanson de Roland").
text_B: Did Charlemagne feel the Basques were his ally?
YES.