British Prime Minister Keir Starmer arrived in Ukraine's capital on Thursday with a pledge to help guarantee the country’s security for a century, days before Donald Trump is sworn in as U.S. president.

While air raid sirens during visits by foreign leaders have sounded before, it is rare for air defenses to actually have to fight off attacking drones.

The British government says Starmer and Ukrainian President Volodymyr Zelensky will sign a “100-Year Partnership” treaty in Kyiv, covering areas including defense, science, energy, and trade.