Wow, using the Explorer to pillage just prior to a war makes a BIG difference.
I had a big civ on my border, crowding and moving in on resources. Their capital was far away. The OLD method of solving this was to build boats, fill them with Cavs or tanks and tote them all the way around the continent, dump them off as close to the capital as possible, start the war, and as quickly as possible, cut the capital off from resources. Of course, the enemy civ would unleash its forces and I'd lose a lot of units. Since this group of units was cut off from reinforcements, they were pretty much a write-off. It would take a couple of turns to cut off the capital, and in the meantime they would have started building resource dependent units which will complete even if I do cut off that resource in a few turns. So I had to fight a much better armed opponant on two fronts.
NOW, with the use of the explorer, I just send in the right amount of explorers right through my enemy's territory..... no boats needed. I pillage every road around the capital. Now, my foe is cut off from resources BEFORE he gets a turn, so no new, powerful units get started! NOW, I am attacking and fighting on one front, and all those units I would have sent on their suicide mission to the capital I now have supported by my nearby territory. Much cheaper, faster and efficient.
I used this strategy against the Russians in a recent game, and since Katherine is always a few tech behind anyway, this invasion felt like the Old Civ2 type of assault, I just swept through. While my Cavalry and bombard units clobbered their cities, my Explorers went around pillaging infrastructure at breakneck speed. It was over very quickly and the only units I lost were a few Explorers.
Using Explorers this way really helps. Thanks for the tip.