[4][5] While stationed in Oituz during the war, he met Elena Negropontes, whom he married in 1918 after divorcing his first wife; their son, Dan Ulise Grigorescu [fr] (1917–1990), became a noted artist and photographer.

[6] The activity carried out in the service of the army was complemented by the activity of a military writer, consisting of memos on various technical matters, reports and miscellaneous memos, as well as two original works: the first - "Calculation of probabilities with application to artillery fire"; conceived in Paris while he was studying mathematics at the Sorbonne and published as soon as he returned to Romania, it was a first, because it was the first time that a Romanian officer addressed a very important problem for artillery; subsequently, the work was submitted to the investigation and approval of the artillery committee and imposed for consultation by all officers and corps; the second - "Ballistic study of the Mannlicher rifle, model 1893", written when he was the Director of the Army Gunpowder Warehouse in Dudești, became a useful tool for infantry and cavalry officers through the useful notions of ballistics and the data related to the characteristics of the respective weapon.

[3]: 145–146 While he was director of the Army Gunpowder Warehouse, he repeatedly refused to accept an order for guncotton (a type of explosive), purchased from the Viennese company "Blumau", because it did not correspond to the specifications.

it became the motto of the entire group of forces that successfully defended the Oituz Valley,[3]: 152  and the great unit earned its nickname of the "Iron Division.

[11] It was there that he achieved his greatest success, managing to defeat Imperial German troops led by General August von Mackensen.

The inscription on his sarcophagus reads: "With the guards at the Gates of Moldavia, who put a stop to the enemy standing as rocks next to me, I wrote in blood on the ridges of Slănic, Oituz, and Cașin: "You cannot pass through here.

"[6] Highly trained military specialist, worthily, courageous military commander, with pragmatic and modern vision in tactical and strategic operations in real war conditions, considered a symbol of Romanian national dignity, General Eremia Grigorescu acquired the honorary title of "Hero of Marăşeşti".

There are also General Eremia Grigorescu streets in Galați, Brăila, Bucharest, Cluj-Napoca, Ploiești Timișoara and many other cities and towns in Romania.

He was the subject of laudatory articles regarding his military merits, in his country ("Neamul Românesc" - 1917, "Mișcarea" - 1917) and abroad ("The Times" and "L'Echo de Paris" - 1917), in the political memoirs of some great commanders of the era (Marshal Joseph Joffre, General John J. Pershing, Marshal von Hindenburg, General Curt von Morgen), and in the works of historians Nicolae Iorga, A. D. Xenopol, Constantin Kiriţescu etc.