In March 2011, he deployed to Afghanistan for duties as commander of the Southwest region.
When he left in March 2012, he was forced to draw down from 20,000 to 7,900 Marines.
"I fought it tooth and nail; said we can't do it, we will lose ground, Afghanistans will lose confidence and will fail and no one will be there to pick them up. I was wrong," he said.
The commanding general of the I Marine Expeditionary Force spoke at the San Diego Military Advisory Council's monthly breakfast inside the Naval Mine and Anti-Submarine Warfare Command on Harbor Drive.
Those 7,900 Marines and Afghans have stood their ground over the past year, Toolan says, thanks to solid leadership among Afghan organizations and units.
"The key in the draw down is providing them enablers," he said.
Those enablers -- which include helicopter, fire and Medivac support -- keep Afghans fighting and Afghan security forces standing watch.
"If we pull [those] away, Afghanistans lose confidence tremendously," he said.
Marines, soldiers and sailors also keep fighting because they know they have the best medical care in the world, he added.
"That makes a huge difference in their confidence. They will go forward in harm's way because they know someone will take care of them," Toolan said.
Military leadership thinks a remaining force of 5,000 to 10,000 people in Afghanistan would be ideal, he said.
"We are not really sure of what the size of the force is going to be," he added.
He is sure, however, that Afghanistan can remain strong despite the shrunken number of U.S. troops.
"I would suspect you will see significant changes by October after this fighting season," he said. "Afghans will definitely be ready. In many ways they are ready now."
For Marines transitioning into the real world, he offered up a streamlined solution to the tedious job-search issue: create an eHarmony or Match.com of sorts for veterans looking for work.
His idea is to condense all job opportunities into one place and match up Marines or sailors with the right fit.
"A lot of guys in [Camp] Pendleton don't stay in San Diego, and there is no national job search capability," he said, adding that the concept is being crafted now.
The Marines' own transition readiness seminar is working to solve the unemployment problem. The five-day program is not just another box that soon-to-be veterans check.
"We are being a lot more serious about it," he said.
Another topic the Marines aren't taking lightly is the suicide epidemic.
There were 349 military suicides in 2012, a 16 percent increase over the previous year, according to statistics from the U.S. Department of the Defense. Forty-eight were Marines.
"I don't just whisk it away as 'this is a cultural thing and the millennial generation.' No," he said. "This is a leadership issue and this requires our attention in a very systematic way."
Each unit is armed with "force preservation counsels" that are tasked with evaluating the lifestyles, work lives and home lives of every Marine that shows any potential problems.
"They go through with a fine-tooth comb the background and history of those folks," he said.
As suicides rise, the concept of mentoring is taking on a new life in the Marine Corps.
"The first question you ask a Marine who has a problem is: ‘Who is your mentor?,'" Toolan said.
While leadership begins at the top, it is most effective at lower levels, he said. That means a staff sergeant, for example, is aware of what is going on in the lives of their Marines and sailors.
Trying to spot potential challenges requires time and effort, he admits.
"It's definitely an issue that is of concern to all Marine Corps leaders and all service units," he said. "Obviously it starts first and foremost with the leadership, and making sure leadership knows their people."
It's not always easy to see signs of suicide.
"That really frustrates us to no end. We then sit leaders down and say, 'What did you see?' Trying to understand it," he said.
Sequestration, across-the-board federal cuts that have been delayed until March 1, is also a cause of stress for the service as a whole. The tightened belt on the defense budget is causing Marines to lose more and more of their capabilities.
"Amphibious ships aren't being built -- at least not the amphibious ships we are used to. Maybe it's time for a sea change. Maybe it's time to open up and say, OK, reality is setting in," he said.
While Marines may not have the latest and greatest amphibious warfare ships to work with, he suggests shifting attention toward uses for littoral combat ships, or small surface vessels.
"Can we do things differently? The answer is yes, and in my estimation, we have to," Toolan said.
Being able to quickly respond to crises throughout the world is a capability they must keep, because if they don't, it could threaten U.S. credibility.
"We are going to have to have forces within the 96-hour ready window to be able to go to places we are needed," he said.