The following Union Army units and commanders fought in the Battle of Cold Harbor (May 31–June 12, 1864) of the American Civil War.
 The Confederate order of battle is listed separately.
 Order of battle compiled from the army organization May 31, 1864, army organization May 26-June 3, 1864, the casualty returns and the reports.
The Battle of Gaines's Mill, sometimes known as the First Battle of Cold Harbor or the Battle of Chickahominy River, took place on June 27, 1862, in Hanover County, Virginia, as the third of the Seven Days Battles (Peninsula Campaign) of the American Civil War.
 Following the inconclusive Battle of Beaver Dam Creek (Mechanicsville) the previous day, Confederate General Robert E. Lee renewed his attacks against the right flank of the Union Army, relatively isolated on the northern side of the Chickahominy River.
 There, Brig. Gen. Fitz John Porter's V Corps had established a strong defensive line behind Boatswain's Swamp.
 Lee's force was destined to launch the largest Confederate attack of the war, about 57,000 men in six divisions.
 Porter's reinforced V Corps held fast for the afternoon as the Confederates attacked in a disjointed manner, first with the division of Maj. Gen. A.P. Hill, then Maj. Gen. Richard S. Ewell, suffering heavy casualties.
 The arrival of Maj. Gen. Stonewall Jackson's command was delayed, preventing the full concentration of Confederate force before Porter received some reinforcements from the VI Corps.
The following Confederate States Army units and commanders fought in the Battle of Cold Harbor (May 31–June 12, 1864) of the American Civil War.
 The Union order of battle is listed separately.
 Order of battle compiled from the army organization during the battle and the reports.
Cold Harbor is an unincorporated community in Hanover County, Virginia.
 The Battle of Cold Harbor was fought in the area in 1864, during the American Civil War.
The 7th Regiment Maryland Volunteer Infantry was a regiment that participated in the American Civil War.
 Edwin H. Webster was one of the regimental commanders.
 This regiment was inducted into service on May 15, 1861.
 After serving guard duty in the defenses of Washington, the regiment was sent to the Shenandoah Valley for operations.
 Their first combat came on March 13, 1863, when they repulsed a charge by the 5th Virginia Infantry regiment.
 They were sent to V Corps, Army of the Potomac.
 At the Battle of Gettysburg, they were forced to withdraw from the Peach Orchard early on the second day.
 They were among the units who repelled Pickett's charge.
 Th unit was stationed for garrison duty in southern Pennsylvania and was involved in skirmishes against some of Jubal Early's infantry units.
 Because of heavy losses at the Battle of Cold Harbor, they were sent as replacements to IV corps, Army of the Potomac.
 They suffered heavy casualties during the Siege of Petersburg, having to repel six charges by counterattacking units of the 15th Georgia Volunteer Infantry.
 They marched in the Grand review and were mustered out of service on June 3, 1865.
Sergeant Terrence Begley (died 25 August 1864) was an Irish soldier who fought in the American Civil War.
 Begley was awarded the United States' highest award for bravery during combat, the Medal of Honor, for his action during the Battle of Cold Harbor in Cold Harbor, Virginia on 3 June 1864.
 He was honored posthumously with the award on 1 December 1864.
The MYH16 gene encodes a protein called myosin heavy chain 16 which is a muscle protein in mammals.
 At least in primates, it is a specialized muscle protein found only in the temporalis and masseter muscles of the jaw.
 Myosin heavy chain proteins are important in muscle contraction, and if they are missing, the muscles will be smaller.
 In non-human primates, MYH16 is functional and the animals have powerful jaw muscles.
 In humans, the MYH16 gene has a mutation which causes the protein not to function.
 Although the exact importance of this change in accounting for differences between humans and other apes is not yet clear, such a change may be related to increased brain size and finer control of the jaw which facilitates speech.
 It is not clear how the MYH16 mutation relates to other changes to the jaw and skull in early human evolution (for example, whether the MYH16 mutation happened first and led to other changes, or whether the MYH16 mutation happened after other changes made the MYH16 protein no longer necessary).
The Battle of Cold Harbor was fought from May 31 to June 12, 1864, with the most significant fighting occurring on June 3.
 It was one of the final battles of Union Lt. Gen. Ulysses S. Grant's Overland Campaign during the American Civil War, and is remembered as one of American history's bloodiest, most lopsided battles.
 Thousands of Union soldiers were killed or wounded in a hopeless frontal assault against the fortified positions of Confederate Gen. Robert E. Lee's army.
During World War II, Operation Grenade was the crossing of the Roer (Rur) river between Roermond and Düren by the U.S. Ninth Army, commanded by Lieutenant General William Hood Simpson, in February 1945.
Franklin Aretas Haskell (July 13, 1828 – June 3, 1864) was a Union Army officer during the American Civil War who was killed during the Battle of Cold Harbor.
 Haskell wrote a famous account of the Battle of Gettysburg that was published posthumously.

Question: Which happened first, Battle of Cold Harbor or Operation Grenade?
Answer: Battle of Cold Harbor