A new American airstrike campaign against Yemen’s Houthi rebels appears more intense and more extensive, as the U.S. moves from solely targeting launch sites to firing at ranking personnel as well as dropping bombs in city neighborhoods,

The Trump administration promised a tougher stance against Yemen’s Houthi rebels, and an Associated Press review of the operation finds its new airstrike campaign appears to be more intense and more extensive.

Houthi rebels said U.S. airstrikes hit Yemen’s capital overnight and into early Monday morning, killing at least three people. Strikes in Sanaa reportedly killed one person, with the Al-Masirah

President Donald Trump has vowed that Houthi rebels in Yemen will be “completely annihilated,” but they have survived previous attacks.

The White House has said that U.S. strikes in Yemen earlier this month killed the Houthi top missile expert, but the U.S. military has so far declined to confirm the death, and the identity of the Houthi commander in question is unclear.

Officials said the new round of strikes in Yemen may last for weeks and that they are now less worried about casualties.

Control represents the prime goal of military strategy, and air bombardment—no matter how relentless—cannot replace the power of boots on the ground.

Trump has ramped up bombing in Yemen to combat the Houthi rebels. But airstrikes alone may take months, if at all, to deter the Iran-armed group.