Flag Parade At Massing Of The Colors

The video covers the 17th annual massing of the colors at the Cathedral, where 12,000 people gathered to honor the men who sacrificed their lives in the nation's wars. The event features a brilliant procession of flags and banners from over 100 civic, veteran, and patriotic groups.

Which groups participated in the procession?

Describe the nature of the procession mentioned in the text.