One of the important issues that voters think about during a presidential election is foreign policy and national security. For Republican nominee Donald Trump, his plans for defending the United States have often resulted in controversy and criticism.

Trump's defense

Since the invasion of Iraq in 2003, the Middle East has been decimated and fractured, as various different Islamic terrorist groups have attempted to control the region. After a poorly U.S. trained Iraqi military lost control of Mosul to the Islamic State (ISIS) in 2014, American-backed forces have been fighting to regain the city ever since.

In recent days, the Iraqi military and other allies have come close to pushing back ISIS' control on the ground, and are expected to be just weeks away before they can rid the city of the terrorist group all together. As expected, Trump has been critical of what has gone down on the ground, as the plan has conflicted with his proposal to "bomb the sh*t" out of oil fields controlled by ISIS. During a sit-down interview with ABC News on Wednesday, Trump elaborated on his thoughts, while also responded to criticism from a retired Army colonel and military expert. The Hill reported further on October 26.

"Trump doesn't know a damn thing about military strategy," Jeff McCausland, former dean at the Army War College, told The New York Times earlier this week.

In response, Trump spoke with George Stephanopoulos of ABC News to voice his opinion. "I’ve been hearing about Mosul now for three months," Trump said, rhetorically asking Stephanopoulos, "Why do they have to say three months before the attack, 'We're going in?'" Trump referred to his strategy as "the element of surprise," before telling Stephanopoulos, You can tell your military expert that I'll sit down and I’ll teach him a couple of things."

This isn't the first time that a military expert has spoken out against Trump.

Earlier this summer, 50 former Republican national security experts came together and released a letter of opposition against the former host of "The Apprentice" due to his views on foreign policy and his unworkable plans.

Campaign countdown

According to the latest Real Clear Politics rolling average, Trump is in trouble on a national level and in swing states.

Hillary Clinton currently leads Trump by just over five points, 48.4 percent to 43 percent, while she's currently projected to hold 252 electoral votes compared to only 126 for the billionaire real estate mogul. Trump's recent slide is not just limited to the presidential race, as many pollsters are now predicting that the Democrats will regain control of the Senate.