They derided his decision to send fewer than 50 troops to northern Syria to "advise and assist" Kurdish and Arab fighters battling ISIS as half-hearted and woefully insufficient.
"I think we have a president who doesn't know what he is doing," Republican presidential hopeful Donald Trump told CNN over the weekend. "You either do it or you don't do it."
House Armed Services Chairman Mac Thornberry, a Texas Republican, warned that, "these steps may prove to be too little, too late."
So can such a small contingent of troops, even if they're from the elite Special Operations units, have an impact? Yes and no.
The White House says these Special Operations forces will be able to assess the situation on the ground and help local fighters with operational planning, tactics and logistics.
"The President does expect that they can have an impact in intensifying our strategy for building the capacity of local forces inside of Syria for taking the fight on the ground to ISIL in their own country," White House Press Secretary Josh Earnest said last week, using another acronym for ISIS.
He also called the elite soldiers an "important force multiplier anywhere around the world they are deployed."
Nicholas Heras of the Center for a New American Security's Middle East Security Program, said that can be true -- and in this case, the small number stands to make the most impact if its deployment is viewed as part of the bigger strategy.
The plan is really about applying a workable strategic model along the lines Earnest outlined that can be scaled up, Heras said.
This deployment is merely the first test to see if the U.S. forces can "play a coordinating role that has an impact on the ground," according to Heras.
By embedding Special Forces with local Sunni anti-ISIS groups, Heras said the administration hopes to build up a multi-ethnic democratic Syrian coalition and facilitate coordination with Kurdish fighters to bring the fight to ISIS.
"This is not going to yield fruit overnight or in the coming weeks," Heras said, highlighting the complicated, socio-political divides between the Kurds and local Syrian forces.
However, Heras said he thinks 50 Special Forces is more than enough to test whether or not this scalable coordinating strategy is an effective model going forward.
Specifically, this first deployment should give defense officials an idea whether U.S. ground troops can facilitate enough strategic coordination between the Kurdish and Syrian groups to pressure ISIS supply lines and reclaim territory around the ISIS stronghold of Raqqa in order to open the possibility of an advance on the city, said Heras.
One of America's primary objectives is to eventually take the key city, a mission that U.S. defense officials say needs to be accomplished primarily by local combat forces.
Heras added that the U.S. mission could also include U.S. Special Ops conducting raids on high-value ISIS targets.
Dakota Wood, a former U.S. Marine now with the Heritage Foundation, agreed that the American military advisers bring significant combat experience that will help increase the effectiveness of the Kurdish forces in areas where ISIS is pushing forward.
But in terms of destroying ISIS outright -- the supreme U.S. objective -- Wood said that 50 Special Operations personnel won't do much in the short term.
Wood argued that the Kurdish forces are chiefly concerned with protecting their territory from ISIS advances but are not interested in extended operations further into Syria.
With the Kurds unwilling to push further into Syria, and the lack of reliable U.S.-backed Syrian militia groups in the region, 50 Special Operations troops would do little on their own to help achieve the administration's ultimate goal of defeating ISIS, according to Wood.
They will do "nothing to really change who controls what ground through greater Syria," he said.