Abu Ishaq said that he was with Sayyidina Zayd ibn Arqam when he was asked about the number of the Prophet’s battles. He said, “They were nineteen ghazwat (battles).” Abu Ishaq asked, “In how many did you participate with him?” He said, “Seventeen.” He asked, “Which was the first?” He said, “Dhat ul-Ushayra” or, he said, “Dhat ul-Usayra.”
[Bukhari 3949, Muslim 1254]