The great army marched to the front in a swelling tide.
Tips
history
The components appear in 《尚书·尧典》 describing the Great Flood: 荡荡怀山襄陵，浩浩滔天 — waters so vast they engulfed hills and reached the sky. Fan Zhongyan fused them in 《岳阳楼记》 as 浩浩荡荡，横无际涯, fixing the form still in use today.
usage
Two core uses: literal vast water (rivers, seas), and vast human movement (armies, processions, crowds). By extension, any unstoppable flow — historical trends, migrations, currents of thought.
