As the news of the execution of another Westerner held hostage by ISIL continue to trickle in, the CIA reports that ISIL's numbers could have at least doubled in recent months after a reassessment of information obtained by the intelligence organization.

The CIA believes ISIL's number of fighters has at least doubled to 20,000 from the original previous estimates of around 10,000, according to The Associated Press. The CIA spokesman who spoke with the news agency said that the number could be as high as 31,500 fighters.

According to Ryan Trapani, the CIA spokesman, the number began to increase in June following ISIL's declaration of a caliphate spanning Syria and Iraq and its advance through Iraq as well as Syria.

He explained the new numbers reflected "greater battlefield activity and additional intelligence," which included reports from May through August.

President Barack Obama already announced earlier this week that the U.S. would continue its fight against ISIL. Now the White House has further revealed its intentions by calling the fight against ISIL "war."

According to the New York Daily News, White House spokesman Josh Earnest has said that the U.S. is at war with ISIL.

"In the same way that we are at war with al-Qaida and its affiliates around the globe, we are at war with ISIL," he said.

Pentagon spokesman Rear Adm. John Kirby reiterated Earnest's message and echoed his statement.

"Make no mistake, we know we are at war with ISIL in the same way we're at war and continue to be at al-Qaida and its affiliates," Kirby said.

In this war, the U.S. has sought the help of allied nations. Germany has shown its support by making illegal any show of ISIL support, according to The New York Times. More than 400 German citizens have joined ISIL and could return to Germany.

However, under the new law all signs of support, including the display of their black flags, are considered illegal. This is an attempt by the government to quell recruitment by the Islamist extremist group.