WASHINGTON—The fight against the self-proclaimed Islamic State could take months or years and requires broad support, a former NATO commander told the Senate Foreign Relations committee Wednesday.

Retired Marine Gen. John R. Allen’s congressional testimony addressed coalition successes, observations from Middle East visits, and goals moving forward as part of the response to the terror tactics of the so-called Islamic State.

President Barack Obama sent a draft authorization for the use of military force against ISIS to Congress on Feb. 12, The administration hopes to clear the way for a military campaign.

While Wednesday’s committee hearing was not specifically intended to address the proposed authorization, Sen. Bob Menendez, D-N.J., immediately acknowledged the panel will “probe” features of current U.S. coalition strategy.

Allen focused on the campaigns against ISIS strongholds in Iraq and Syria; and senators’ questions also touched on Turkey’s efforts to stop fighters crossing into Syria.

The retired general also addressed the current coalition “multiple lines of effort,” intended to disrupt ISIS finances and the flow of foreign fighters among other goals.

What became the main theme—tied to the military force debate—was an asserted lack of specifics in the president’s proposal.

Sen. Ron Johnson, R-Wis., for example, asked for details of plans aimed at stopping the operational capability of ISIS. Allen mentioned a plan to break the organization into small groups. But when Johnson requested numbers and specifics, he didn’t get them.

One clear issue was the ongoing social media campaign by ISIS. Allen said that although free speech can be an obstacle on some platforms, the U.S. is working with industry to remove the propaganda.

The Republican majority seemed to favor giving the president a broad capacity to use any military means deemed necessary. The Democrats were more concerned with the time and troop numbers that the term “enduring” would levy.

Menendez even went so far as to say he believes use of ground forces would “decisively increase the prospect of losing” a drawn-out war.

Although the president’s proposed authorization would expire in three years, some committee members were not satisfied. Considering the resolution would carry into the next presidency, it’s also a possible campaign topic.

Other members of the committee include 2016 GOP presidential hopefuls Sen. Rand Paul of Kentucky and Sen. Marco Rubio of Florida.