Retired Gen. David D. McK­iernan, the former com­mander of U.S. and NATO forces in Afghanistan, used the familiar New Eng­land imagery of a lob­ster pot to describe the ram­i­fi­ca­tions of U.S. mil­i­tary inter­ven­tion in con­flicts on for­eign soil.

Easy to get in,” but “hard to get out,” he told a packed Raytheon Amphithe­ater at North­eastern Uni­ver­sity on Thursday evening.

The event, enti­tled “U.S. Mil­i­tary Inter­ven­tions, Pre– and Post-​​9/​11,” aligned with Northeastern’s com­mit­ment to national secu­rity and the goal of fos­tering dis­cus­sions of great global impor­tance. It was co-​​sponsored by the Office of the Pres­i­dent and Col­lege of Social Sci­ences and Human­i­ties.

Throughout the 90-​​minute, candid dis­cus­sion McK­iernan stressed that U.S. mil­i­tary inven­tion should be a last resort in responding to inter­na­tional con­flicts. He said Amer­ican polit­ical leaders must also place a greater pri­ority on under­standing the his­tory, cul­ture and com­plex social struc­ture of those regions, in addi­tion to the diver­sity of people living there. Those steps, he said, weren’t given proper con­sid­er­a­tion before America sent troops to Iraq and Afghanistan in the wake of the Sept. 11 attacks.

McK­iernan urged stu­dents in atten­dance to keep these con­sid­er­a­tions in mind as they pre­pare to begin careers in which they’ll be required to make impor­tant decisions.

It requires the intel­lec­tual energy of every­body to make good deci­sions,” he said. “We’ve made some good deci­sions, and we’ve made some bad deci­sions. Under­standing the envi­ron­ment is key to making those good deci­sions.” After his lec­ture, McK­iernan fielded ques­tions posed by audi­ence mem­bers on topics such as the use of drones in combat, applying lessons learned from past con­flicts to cur­rent dilemmas and the finan­cial costs of war.

McK­iernan, the former com­mander for the Inter­na­tional Secu­rity Assis­tance Force in Afghanistan, entered the Army in 1972 with an ROTC com­mis­sion and com­manded sol­diers at every rank from second lieu­tenant to four-​​star gen­eral. His dis­tin­guished 37-​​year U.S. Army career included ser­vice in the Gulf War, Korea, Europe and the Balkans, South­west Asia, Iraq and Afghanistan.

McK­iernan led all ground forces into Iraq during Oper­a­tion Iraqi Freedom in 2002-​​03, removing Saddam Hus­sein and the Baath Party from power with a 160,000 joint and coali­tion for­ma­tion. In his final com­mand assign­ment in 2008-​​09 in Afghanistan, he was respon­sible for more than 100,000 sol­diers, sailors, airmen, Marines and Spe­cial Forces in both a NATO ISAF (including 42 con­tributing nations) and U.S. Oper­a­tion Enduring Freedom role.

In his Thursday evening dis­cus­sion, McK­iernan focused on U.S. mil­i­tary inter­ven­tions in Iraq and Afghanistan, but also touched on Amer­i­cans’ pres­ence in both mil­i­tary and peace-​​keeping roles dating back to the Cold War and in places such as Kuwait, Panama and Kosovo.

It’s a much more com­plex, ambiguous, divi­sive world when you decide to go in and inter­vene some­where and change the status quo, change the existing order,” he said.

He added, “Unless we’re willing to pledge a siz­able of amount of resources to commit mil­i­tary for a long period of time, I’m talking gen­er­a­tions, there won’t be a lasting impact, espe­cially if there’s not pop­ular sup­port in the area where we’ve intervened.”

ROTC cadets listen to retired Gen. David D. McK­iernan speak Thursday in Raytheon Amphitheater.

Ear­lier in the day, McK­iernan engaged more than 50 people for a seminar-​​style lec­ture focused on Afghanistan, which he described as a country with a “mosaic” of people who’ve lived through a his­tory of con­tinual con­flict — one that has trau­ma­tized its social fabric and bred a cul­ture of violence.

The seminar’s audi­ence com­prised of fac­ulty, staff, ROTC cadets, mem­bers of the Stu­dent Vet­erans Asso­ci­a­tion and under­grad­uate stu­dents in the “Inter­na­tional Con­flict and Nego­ti­a­tion” course taught by Kim­berly Jones, fac­ulty asso­ciate in the Middle East Center for Peace, Cul­ture and Devel­op­ment and head adviser in the Inter­na­tional Affairs pro­gram and Middle East Studies.

At the after­noon dis­cus­sion, Georges Van Den Abbeele, founding dean of the Col­lege of Social Sci­ences and Human­i­ties, high­lighted McKiernan’s dis­tin­guished career and wel­comed him back to campus. McK­iernan served as the keynote speaker at Northeastern’s Vet­erans Day cer­e­mony in 2011 hon­oring those who have served and pro­tected our country.

Van Den Abbeele also noted Northeastern’s com­mit­ment to lead­er­ship in national-​​security efforts, including its long­standing com­mit­ment to the ROTC pro­gram.

I saw first hand the tremen­dous exper­tise and expe­ri­ence Gen­eral McK­iernan can bring to the uni­ver­sity com­mu­nity, and par­tic­u­larly to the Col­lege of Social Sci­ences and Human­i­ties, when I heard him speak on campus last fall,” Van Den Abbeele said. “He did not dis­ap­point in Pro­fessor Jones’ class this morning. Our stu­dents had the unique oppor­tu­nity to learn from and engage with one of the most dis­tin­guished com­man­ders of our times, a strategic thinker whose grasp of the global chal­lenges we face today is simply unparalleled.”