The most tangible sign that relations between enemies are improving is when transport links are restored. Such has been the case with China and Vietnam, India and Pakistan and yesterday, North and South Korea.
There was much symbolism in the cargo train that crossed the Korean border from South to North, heading for the jointly developed industrial zone at Kaesong. The daily, 16.5km round trip represents implementation of agreements, growing economic and diplomatic co-operation, aspirations for progress on outstanding issues and, above all, a hope that the two Koreas will one day again become one.
Dozens of cars, trucks and buses already cross the border each day on reconnected roads to Kaesong and a mountain tourism resort. The first regular rail service since the line was severed by the Korean war in 1951 has significantly greater meaning, though. Although South Korea is on a peninsula, travel to the mainland can be made only by air or sea. This effectively makes the South an island - a sense exacerbated by the country being sandwiched between China and Japan.
Rail links hooking the South, through North Korea, to China and Russia and consequently Europe, would create an outlet for cheaper transport of goods and further spur impressive industrial growth. But while the resumption moves the process of conciliation forward, it is only a small part of the process. In only the second meeting ever of Korean leaders, deals were struck in October for the joint development of port facilities in the northern city of Haeju, shipbuilding projects and the opening of direct flights between the South and Mount Paektu, by legend the ancestral home of the Korean people. This came amid continued efforts to ensure Pyongyang complied with a February deal to scrap its nuclear weapons programme.
South Korea is committed to peace and reuniting the Korean Peninsula. Doing so has benefits for both Koreas. If the promise afforded by yesterday's resumed rail service is to be realised, Pyongyang must live up to its side of the bargain and implement the agreements it has signed.