The ‘Darkhorse’ Marines are not actually in combat right now

SUMMARY
Although thousands upon thousands of well-meaning Americans on Facebook and Twitter are asking people to pray for the 3rd Battalion, 5th Marine Regiment, the grunts aren't suffering any casualties in Afghanistan. They're home at Camp Pendleton, preparing to deploy to sea.
The latest hoax seems to have broken out on Facebook in late February before dying down in mid-March. It has come roaring back in recent days, however, triggering a flood of social-media support for the "Darkhorse" battalion that once suffered heavy losses in Afghanistan but isn't actually in combat now.
"We are asking everyone to say a prayer for 'Darkhorse' 3rd Battalion, 5th Marines and their families. They are fighting it out in Afghanistan and have lost nine Marines in four days. Please repost this," reads the typical message being circulated on social media.
As the rumors circulated in March and April, the battalion was training for a future deployment with the 15th Marine Expeditionary Unit. Between March 24 and April 4, for example, 3/5 Marines underwent a Marine Corps Combat Readiness Evaluation at Camp Pendleton.
This week, elements of the 15th Marine Expeditionary Unit have been participating in a Composite Unit Training Exercise — "COMPTUEX" — off the coast of Southern California aboard the Navy's amphibious assault ship America.
The urban legend about 3/5 Marines currently suffering major combat losses in Afghanistan has roots in truth.
Deployed to Afghanistan's restive Helmand Province in 2010-11, 3/5 Marines and the 1st Combat Engineers suffered 25 deaths and nearly 200 wounded. Some of the most brutal fighting was concentrated near the district of Sangin, triggering widespread support on the social media from well-wishers at the time.
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After the Darkhorse Marines rotated home, calls for prayers for their safety continued to flare up in late 2012, both the summer and late winter of 2013, the summers of 2014 and 2015, late December of 2015 and then again two months ago, according to a San Diego Union-Tribune analysis of Facebook and Twitter feeds.
Twitter and Facebook followers often have demanded to know why the "mainstream media" or "MSM" refused to cover the old story, failing to realize that the Union-Tribune and other news outlets reported extensively about the Darkhorse battalion's real deployment of 2010-11 in Afghanistan.
Internet rumor-slayer Snopes.com updated a special page on the Darkhorse dilemma on May 1, pointing to articles about the earlier deployment in the Union-Tribune and its sister paper the Los Angeles Times. Snopes rated the latest eruption of 3/5 prayer requests "outdated."