allegiance (n)
/əˈli·dʒəns/

support for a leader, country, group, or belief

artillery (n)
/ɑrˈtɪləri/

large heavy guns, which are often moved on wheels

battle (v)
/ˈbæt̬·əl/

to try very hard to deal with a difficult situation

cease (v)
/sis/

to stop an action or condition

hierarchy (n)
/ˈhɑɪ·əˌrɑr·ki/

system in which people or things are put at various levels or ranks according to their importance

in the trenches (phrase)
/ɪn ðə trentʃ/

a long, deep hole dug in the ground in which soldiers can be protected from enemy attacks

mobilize (v)
/ˈmoʊ·bəˌlɑɪz/

to find and start to use something that is needed for a particular purpose

low-ranking (a)
/loʊ ˈræn.kɪŋ/

junior; not very important

ratio (n)
/ˈreɪ·ʃIˌoʊ/

a comparison of two numbers calculated by dividing

strategic (a)
/strəˈtiː.dʒɪk/

used to provide military forces with an advantage

medicine (n)
/ˈmed·ə·sɪn/

a substance that you take to treat an illness, especially a liquid that you drink

combat (n)
/ˈkɑm·bæt/

fighting during a time of war

military (a)
/ˈmɪl·ɪˌter·i/

connected with soldiers or the armed forces

camp (n)
/kæmp/

a place where soldiers live while they are training or fighting

mosquito (n)
/məˈskiː.t̬oʊ/ 

a small flying insect that bites people and animals and sucks their blood

plague (v)
/pleɪɡ/

to cause someone or something difficulty or suffering, esp. repeatedly or continually

vaccinate (v)
/ˈvæk·səˌneɪt/

to give someone a vaccine, usually by injection, to prevent them from getting a disease

smallpox (n)
/ˈsmɔlˌpɑks/

an extremely infectious viral disease that causes fever, spots on the skin, and often death

obey (v)
/oʊˈbeɪ/

to do what a law or a person says that you must do

troop (n)
/trup/

a group of soldiers or police, esp. one equipped with horses