On Feb­ru­ary 28, Major Ander­son sought his offi­cers’ assess­ments on the required per­son­nel and ships to rein­force Fort Sumter for sub­mis­sion to the War Depart­ment and Pres­i­dent Lin­coln. He instruct­ed each offi­cer to pro­vide their esti­mates autonomous­ly, hop­ing that the daunt­ing real­i­ties of rein­force­ment would dis­suade the gov­ern­ment from pur­su­ing aggres­sive action.

Cap­tain Fos­ter, the chief engi­neer, report­ed the high­est esti­mate: land­ing and secur­ing the bat­ter­ies at Cum­mings Point and Mor­ris Island would neces­si­tate 3,000 reg­u­lars or 10,000 vol­un­teers, with an addi­tion­al 3,000 reg­u­lars required for Sul­li­van’s Island. To main­tain con­trol over these posi­tions after­ward, a force of 10,000 reg­u­lars or 30,000 vol­un­teers would be essen­tial. The antic­i­pat­ed resis­tance would come from South Car­olini­ans, bol­stered by troops from neigh­bor­ing states.

Artillery Cap­tain Tru­man Sey­mour pre­sent­ed an even graver eval­u­a­tion. He assert­ed that resup­ply mis­sions via deceit were no longer fea­si­ble due to height­ened vig­i­lance, stat­ing that open attempts would fail unless ves­sels were imper­vi­ous to gun­fire. Such efforts would draw imme­di­ate atten­tion, and any siz­able Union troop move­ment toward Fort Sumter would pro­voke a swift Con­fed­er­ate response, con­sol­i­dat­ing sub­stan­tial local resources against an invad­ing force. Sey­mour warned of the pos­si­bil­i­ty of twen­ty thou­sand trained marks­men assem­bling to defend Charleston Har­bor, which he likened to the siege of Sev­astopol, pre­dict­ing cat­a­stroph­ic loss­es.

Oth­er offi­cers con­tributed esti­mates for a nec­es­sary invad­ing force vary­ing between three thou­sand and ten thou­sand men, all requir­ing mar­itime pro­tec­tion. Quar­ter­mas­ter Hall sug­gest­ed deploy­ing sev­en war­ships, although he cau­tioned that suc­cess would hinge on improb­a­ble cir­cum­stances and a like­ly fail­ure was more prob­a­ble.

Ander­son relayed these assess­ments to Wash­ing­ton, care­ful to express his con­cur­ring view that an effec­tive attempt to rein­force the fort would need at least twen­ty thou­sand well-trained troops. This rec­om­men­da­tion implied the need for a force larg­er than the entire U.S. Army at that time, demon­strat­ing the immense chal­lenge posed by rein­forc­ing Fort Sumter amidst the loom­ing con­flict.