This is one of my favorite theories behind atla and I wanted to share my own breakdown of it.

SO the raids on the SWT began in 40 AG. They continued until each and every waterbender from the Southern Water Tribe had been captured. (Note: captured)

Worth noting is that Hama refers to herself as the last waterbender of the Southern Water Tribe.

Here’s where the conspiracy gets juicy. Hama was the only one who managed to escape. She created bloodbending to get out of the prison. And she says herself that she’s the only one who escaped. This could be for one of two reasons:

All of the other prisoners had already succumb to the conditions or been killed The remaining waterbender prisoners were murdered after Hama’s escape

The second option is more plausible. Hama displayed a dangerous, powerful, unknown form of waterbending and overtook a Fire Nation guard’s body. She had him unlock her cell and fled. If there were remaining waterbenders in the prison they would have been killed out of fear once Hama escaped.

They Fire Nation couldn’t risk anyone else in their prison possessing this power. So they were all murdered because of Hama’s escape.

Look at Hama’s reaction to hearing that the raids continued. A kind of casual “oh, you poor things.” Hama knew that the raids continued because she escaped. All of the waterbenders had already been caught! The only waterbender of the Southern Water Tribe that was known at that time to be free or alive was Hama.

And she knew better than to return to her home, where they were sure to come looking for her. She stayed and hid right under their noses because she knew they were going to tear the world apart trying to track her down. She was too dangerous.

When Yon Rha comes to the Southern Water Tribe in 94 AG Katara is still a child. Their tribe has been in shambles for years at this point. Katara is the tribe’s last hope and they’re a tiny tribe at that point in time. Do you honestly think that word of a child waterbender would have made way to the Fire Nation?

Do you think that the Water Tribe would ever release that information willingly? I don’t. I think that the Southern Raiders had no idea that another waterbender had been born into the Southern Water Tribe.

Why else would Yon Rha have accepted that an adult was the waterbender he was looking for? The intel didn’t say that a new waterbender was born, the intel said that there’s one waterbender left. The Fire Nation already knows about the last waterbender of the SWT. She escaped. And they’re still trying to find her.

The Fire Nation is adamant about finding the last waterbender because they’re looking for Hama. Hama, who can control people’s bodies. Hama, who managed to escape a high-security Fire Nation prison without any water. Hama, the only waterbender to best the Fire Nation. And the only one left.

Kya offers herself up as prisoner to Yon Rha. Because she knows that the past raids meant that the Southern Raiders took the waterbenders prisoner. But that has changed.

Why would their procedure have changed? Why did they stop taking waterbenders as prisoners? Because of Hama. They stopped taking waterbenders prisoner after Hama’s escape.

Tl;dr the Southern Raiders were never looking for Katara, they were looking for Hama.