Wikipedia states:
French Horns tend to always carry the rhythmic backup of a march. For example, in cut-time marches, they are typically assigned upbeats (the + of 1 and 2) to provide the "pah" for the stylistic "oom-pah" sound. In 6/8 marches, French horns play on beat 1, the 'li' of 1, beat 2, and the 'li' of 2 (1-la-li 2-la-li). In other words, the measure would be one eighth note, then an eighth rest, then two eighth notes, an eighth rest, then a final eighth note.
However, what beats would the horn normally play on in a 2/4 march, the other major type? Is it the second?