Alma 53:13

But it came to pass that when they saw the danger, and the many afflictions and tribulations which the Nephites bore for them, they were moved with compassion, and were desirous to take up arms in the defence of their country.

But when they saw the danger and all the hard times the Nephites went through for them, they felt sorry for the Nephites. They wanted to pick up weapons to defend their country.

But when they saw the danger the Nephites faced, and all the hardship and suffering the Nephites were enduring on their behalf, they were moved with compassion. They wanted to take up weapons to defend their adopted country.