POCHEON, South Korea (AP) — A huge North Korean flag disappeared behind a tower of flames and thick black smoke today as South Korean fighter jets and U.S. attack helicopters fired rockets in the allies’ biggest joint live-fire drills since the Korean War.

The war games south of the heavily armed Korean border come amid rising animosity between the rival Koreas and are meant to mark Monday’s 62nd anniversary of the start of the 1950-53 war, which ended in a truce, leaving the Korean Peninsula still technically at war.

Live-fire drills by the allies are fairly routine, but using the North’s national flag as part of target practice is unusual — and will be seen as a provocation by Pyongyang, which has previously threatened war for what it called South Korean insults to the country’s national symbols and leadership.

Still, an immediate North Korean military retaliation is unlikely. The rockets didn’t hit the flag, which an analyst said might lead to a less angry North Korean response. But even a direct attack on the flag would probably only result in escalated North Korean threats because Pyongyang’s struggling economy prevents it from staging any attack that could cause a war, said Koh Yu-hwan, a North Korea professor at Seoul’s Dongguk University.