rear guard

基本解释

These stubborn and skilful rear guard actions checked the impetuous German advance at all points , inflicting severe losses.
这几场打得顽强而巧妙的后卫战，在各个方面都阻止了猛扑过来的德军，使他们遭受严重的损失。
The remaining two alien formations fired upon this Covenant rear guard—energy beams cut their shields and blasted them to atoms.
其余的队列继续向圣约人舰队的后卫开火。能量束切开他们的护盾，把他们烧成原子。
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Unnerved by sharp counterattacks delivered by the outnumbered Confederate rear guard, Hooker squandered his advantage by halting to erect defenses near the Chancellor farm.
受挫于数量不及自己的邦联军后卫猛烈的反击，Hooker 将军平白浪费了自己兵力上的优势而在 Chancellor 农场驻军建立防御工事。

And finally the rear guard, aka: the old farts.
FORBES: VOIP Tipping Point
One of several problems that delayed the formation of the new government was the rear guard action waged by the Shiite Fadila Party to hang onto the Oil Ministry, which it controlled under former Prime Minister Ibrahim al-Jafari.
NPR: Iraq Oil Minister Vows to Fight Corruption, Smuggling
What about the rear guard?
FORBES: VOIP Tipping Point

In a battle, the rearguard is a group of soldiers who protect the back part of an army, especially when the army is leaving the battle.
If someone is fighting a rearguard action or mounting a rearguard action, they are trying very hard to prevent something from happening, even though it is probably too late for them to succeed.