Bets on Houthi forces entering Saudi Arabia by year-end fall, and the reason is unclear

Traders sharply lowered their expectations on Monday that Houthi military forces will enter Saudi Arabia before the end of the year. They now see it as unlikely, after treating it as a toss-up earlier in the day.

The cause of the drop is not clear. No report or development has been identified as the reason, and the timing of the day's news does not establish one. The slide came in a matter of minutes on Monday evening, after a brief rebound earlier in the evening had pushed expectations back toward a toss-up.

The question covers only a deliberate operation by Houthi forces, including any armed force acting on their behalf, inside Saudi territory, even a temporary one. Credible reporting must establish that entry. Bombardment, sabotage, offshore naval presence, and any threat or claim of entry do not count. Neither do prisoners of war or emissaries negotiating agreements.

The conflict between Saudi Arabia and the Houthis has intensified in recent weeks. The Houthis advanced along Yemen's Red Sea coast in September. On September 15, a United Nations official told the Security Council that Yemen's government had launched a counteroffensive. He also condemned Houthi cross-border attacks on Saudi civilian and energy infrastructure.

The Associated Press reported on Sunday that Syria was preparing to send fighters to Saudi Arabia's border, citing three officials familiar with the plans. On Monday, Yemeni government forces claimed fresh gains against the Houthis in Lahj province, according to Al Jazeera, while the Houthis kept up missile and drone attacks toward Saudi Arabia. Saudi Arabia also said its East-West oil pipeline was targeted on Monday, causing a small fire. Attacks of that kind fall short of what the question requires.

Fighting and cross-border attacks are continuing. A yes outcome would need a consensus of credible reporting that Houthi forces deliberately crossed into Saudi territory before the end of the year. Reports of border deployments and shifts in the front lines will matter most in the coming weeks.