We went on two military expeditions with the Messenger of Allah ﷺ during Ramadan, the day of Badr and the Conquest, and we broke our fast on both of them.
غزونا مع رسول الله ﷺ في رمضان غزوتين: يوم بدر والفتح، فأفطرنا فيهما.
Tirmidhi (714) narrated it from Qutayba, who said, Ibn Lahia related to us, from Yazid bin Abu Habib, from Muammar bin Abu Habib, from Ibn Musayab, that he was asked about fasting while traveling. He related that Umar bin Khattab said, and then mentioned it. Ibn Lahia is in the chain, but Qutayba's narration from him was before his memory became confused. Imam Ahmad (142) also narrated it, from Hasan bin Musa, from Ibn Lahia, with his chain, similarly. He also narrated it (140) from Abu Saeed, who is Amr bin Muhammad Anqari, from Ibn Lahia, who said, Bukayr related to us, from Saeed bin Musayab, from Umar, and he mentioned it similarly. This contains a corroborating report supporting Yazid bin Abu Habib.As for whether Saeed bin Musayab actually heard from Umar bin Khattab, this is disputed, and the more correct view is what Imam Ahmad said, "He saw him and heard from him. If Saeed's report from Umar is not accepted, then whose would be?"See, Al-Jarh wal-Tadil (4/61).