special correspondent jane ferguson reports from special correspondent jane ferguson reports from thentlines, near makhmour, iraq. >> reporter: in an effort to soften isis positions, iraqi forces bombard them repeatedly. they are trying to push forward from this sandbank, up the hill to a village islamic state fighters are dug into. last week, the iraqi army suddenly announced the launch of the long-awaited battle for mosul city. in reality, so far just several villages have been re-taken in the makhmour area, well south of mosul. this is as far as the front line comes for these iraqi troops. they are mortaring the village in that direction that is just on that hill. that's where isis positions are. that village is called al nasr. they plan to then move in and try to occupy the village but they have been trying to do that for three days. far beyond that village is the city of mosul, and bit-by-bit, inch-by-inch, they plan to re- take it. so far, progress is slow. iraqi forces swiftly abandoned their positions here in 2014, when isis swept across the country. morale in the military has

for the pbs newshour, i'm jane ferguson in erbil, iraq. >> woodruff: meanwhile, the syrian government announced its troops have fought their way into palmyra, with support from russian air strikes. the roman-era city is held by islamic state fighters and lies at a key crossroads in central syria. state tv today showed military units entering the outskirts of palmyra. but they're too late to save ancient temples, tombs and other artifacts already destroyed by the militants. secretary of state john kerry and russian president vladimir putin talked up prospects for peace in syria today. the two men met in moscow. kerry welcomed russia's withdrawal of most of its military forces from syria. putin said u.s./russian cooperation has helped bring progress. meanwhile, the latest round of syrian peace talks ended in geneva. they're to resume april 9. president obama spent a final day in argentina, paying tribute to victims of brutal, military rule. and, he acknowledged the united states was slow to condemn it. he visited a memorial to thousands killed in the so- called "dirty war," from 1976 to

for the pbs newshour, i'm jane ferguson, in northern iraq. >> woodruff: back to this country, and thepresidential race. we want to take a closer look at significant issues shaping the campaigns. tonight: immigration. the plans for reform range from a tall border wall funded by mexico, to a path to citizenship for the 11 million undocumented immigrants living here now. we dig into the issue and the role of latino voters with mark krikorian, executive director of the center for immigration studies, and author of the book, "the new case against immigration, both legal and illegal." frank sharry, founder of the immigration reform group america's voice, and brittney parker, a senior officer at the commonwealth foundation, a nonpartisan, nonprofit think tank that promotes free market ideas. and we welcome all three of you to the news hour. mark krikorian, let me start with you first. let's talk about the republican candidates for president. what are they saying? how are they differing at this point you have ted cruz, donald trump and john kasich. how do they differ on the subject of immigra